<PAGE>

                                                                    EXHIBIT 10.1

                       FIRST AMENDMENT TO CREDIT AGREEMENT

         THIS FIRST AMENDMENT TO CREDIT AGREEMENT, dated as of December 15, 2003
(this "Amendment"), amends the Credit Agreement, dated as of December 16, 2002
(the "Credit Agreement"), among DELPHI FINANCIAL GROUP, INC., a Delaware
corporation (the "Borrower"), the various financial institutions parties thereto
(collectively, the "Lenders") and BANK OF AMERICA, N.A., as administrative agent
(the "Administrative Agent") for the Lenders. Terms defined in the Credit
Agreement are, unless otherwise defined herein or the context otherwise
requires, used herein as defined therein.

         WHEREAS, the parties hereto have entered into the Credit Agreement,
which provides for the Lenders to extend certain credit facilities to the
Borrower from time to time; and

         WHEREAS, the parties hereto desire to amend the Credit Agreement in
certain respects as hereinafter set forth;

         NOW, THEREFORE, in consideration of the premises and for other good and
valuable consideration (the receipt and sufficiency of which are hereby
acknowledged), the parties hereto agree as follows:

         SECTION 1. AMENDMENTS. Effective as of the date hereof, the Credit
Agreement shall be amended in accordance with Sections 1.1 through 1.16 below.

         1.1      Deleted Definitions. The definitions of "Borrower Pledge
Agreement," "Collateral," "Collateral Agent," "Intercreditor Agreement," "Pledge
Agreements," "SIG Holdings Pledge Agreement," and "SIG Notes Pledge Agreement"
in Section 1.01 of the Credit Agreement are hereby deleted.

         1.2      Loan Documents. The definition of "Loan Documents" in Section
1.01 is hereby amended to state in its entirety as follows:

                  "Loan Documents" shall mean this Agreement, each Note and the
                  Fee Letter.

         1.3      Maturity Date. The definition of "Maturity Date" in Section
1.01 of the Credit Agreement is hereby amended by the deletion of the date
"December 16, 2005" and the substitution of the date "December 16, 2006"
therefor.

         1.4      Related Documents. The definition of "Related Documents" in
Section 1.01 of the Credit Agreement is hereby amended to state in its entirety
as follows:

                  "Related Documents" shall mean the Notes, if any, the Tax
                  Sharing Agreements, and any and all other documents or
                  instruments furnished or required to be furnished pursuant to
                  or Article V, as the same may be amended or modified from time
                  to time.
<PAGE>

         1.5      Collateral. Article 4 of the Credit Agreement is hereby
deleted and intentionally left blank.

         1.6      Conditions Precedent. Section 5.01(a)(i) of the Credit
Agreement is hereby amended to state in its entirety as follows:

                  "(i) executed counterparts of this Agreement, sufficient in
                  number for distribution to the Administrative Agent, each
                  Lender and the Borrower."

         1.7      Collateral Representation. Section 6.16 of the Credit
Agreement is hereby deleted and intentionally left blank.

         1.8      Pledged Shares. Section 6.26 of the Credit Agreement is hereby
deleted and intentionally left blank.

         1.9      Other Information. Section 7.01(w) of the Credit Agreement is
hereby amended to state as follows:

                  "(w) Other Information. From time to time such other
                  information and certifications concerning the Borrower and any
                  of its Subsidiaries as the Administrative Agent or a Lender
                  may reasonably request."

         1.10     Further Assurances. Section 7.11 of the Credit Agreement is
hereby deleted and intentionally left blank.

         1.11     Liens. Section 8.01(a) of the Credit Agreement is hereby
deleted and intentionally left blank.

         1.12     Liens - Investments. Section 8.01(i) of the Credit Agreement
is hereby amended to state in its entirety as follows:

                  "(i) Liens incurred in connection with the acquisition of
                  Investments permitted by this Agreement."

         1.13     Change of Location. Section 8.12 of the Credit Agreement is
hereby deleted and intentionally left blank.

         1.14     Ownership of RSL; SIG Holdings and Safety National. Section
8.15 of the Credit Agreement is hereby amended to state in its entirety as
follows:

                  "(a) Ownership of RSL; SIG Holdings and Safety National. Not
                  cease to own, free and clear of all Liens, 100% of the
                  outstanding shares of voting stock of RSL-Texas on a fully
                  diluted basis, except as a result of any merger,
                  consolidation, liquidation or dissolution referenced in clause
                  (a) of the definition of Change of Control; (b) Not permit
                  RSL-Texas to cease to own, free and clear

                                       2
<PAGE>

                  of all Liens, 100% of the outstanding shares of voting stock
                  and voting power of RSL on a fully diluted basis, except as a
                  result of any merger, consolidation, liquidation or
                  dissolution referenced in clause (a) of the definition of
                  Change of Control, whereafter this clause (b) shall apply to
                  the Borrower rather than to RSL-Texas; (c) not cease to own,
                  free and clear of all Liens, 100% of the outstanding voting
                  stock and voting power of SIG Holdings and (d) not permit SIG
                  Holdings to cease to own, free and clear of all Liens, 100% of
                  the outstanding shares of voting stock and voting power of
                  Safety National on a fully diluted basis."

         1.15     Risk-Based Capital Ratio. Section 8.18 of the Credit Agreement
is hereby amended by the deletion of the number "130%" and the substitution of
the number "110%" therefor.

         1.16     Collateral Matters. Section 10.11 of the Credit Agreement is
hereby deleted and intentionally left blank.

         1.17     Amendments. Section 11.01(g) of the Credit Agreement is hereby
deleted and intentionally left blank.

         1.18     Confidentiality. Section 11.08 of the Credit Agreement is
hereby amended by the addition of the following at the end:

                  Notwithstanding anything herein to the contrary, except as
                  reasonably necessary to comply with applicable securities
                  laws, each party (and each employee, representative or other
                  agent of each party) hereto may disclose to any and all
                  Persons, without limitation of any kind, any information with
                  respect to the United States federal income "tax treatment"
                  and "tax structure" (in each case, within the meaning of
                  Treasury Regulation Section 1.6011-4) of the transactions
                  contemplated hereby and all materials of any kind (including
                  opinions or other tax analyses) that are provided to such
                  parties (or their representatives) relating to such tax
                  treatment and tax structure; provided that with respect to any
                  document or similar item that in either case contains
                  information concerning the tax treatment or tax structure of
                  the transaction as well as other information, this sentence
                  shall only apply to such portions of the document or similar
                  item that relate to the United States federal income tax
                  treatment or tax structure of the transactions contemplated
                  hereby.

         1.19     Schedule 2.01. Schedule 2.01 to the Credit Agreement is hereby
amended to state as set forth on Schedule 2.01 hereto.

         1.20     Exhibits. Exhibits F, G and H of the Credit Agreement are
hereby deleted and intentionally left blank.

                                       3
<PAGE>

         SECTION 2. CONDITIONS PRECEDENT. This Amendment shall become effective
when each of the conditions precedent set forth in this Section 2 shall have
been satisfied, and notice thereof shall have been given by the Administrative
Agent to the Borrower and the Lenders.

         2.1 Receipt of Documents. The Administrative Agent shall have received
all of the following documents duly executed, dated the date hereof or such
other date as shall be acceptable to the Administrative Agent, and in form and
substance satisfactory to the Administrative Agent:

                  (a)      Amendment. This Amendment, duly executed by the
         Borrower, the Administrative Agent and the Lenders.

                  (b)      Secretary's Certificate. A certificate of the
         secretary or an assistant secretary of the Borrower, as to (i)
         resolutions of the Board of Directors of the Borrower then in full
         force and effect authorizing the execution, delivery and performance of
         this Amendment and each other document described herein, and (ii) the
         incumbency and signatures of those officers of the Borrower authorized
         to act with respect to this Amendment and each other document described
         herein.

         2.2 Compliance with Warranties, No Default, etc. Both before and after
giving effect to the effectiveness of this Amendment, the following statements
by the Borrower shall be true and correct (and the Borrower, by its execution of
this Amendment, hereby represents and warrants to the Administrative Agent and
each Lender that such statements are true and correct as at such times):

                  (a)      the representations and warranties set forth in
         Article 6 of the Credit Agreement shall be true and correct with the
         same effect as if then made (unless stated to relate solely to an
         earlier date, in which case such representations and warranties shall
         be true and correct as of such earlier date); and

                  (b)      no Default shall have then occurred and be
         continuing.

         2.3 Amendment Fee. The Borrower shall have paid to the Administrative
Agent for the account of the Lenders, based on their Pro Rata Shares, an
amendment fee of 0.15% of the Aggregate Commitments.

         SECTION 3. REPRESENTATIONS AND WARRANTIES. To induce the Lenders and
the Administrative Agent to enter into this Amendment, the Borrower hereby
represents and warrants to the Administrative Agent and each Lender as follows:

         3.1 Due Authorization, Non-Contravention, etc. The execution, delivery
and performance by the Borrower of this Amendment are within the Borrower's
corporate powers, have been duly authorized by all necessary corporate action,
and do not

                  (a)      contravene the Borrower's Organization Documents;

                                       4
<PAGE>

                  (b)      contravene any contractual restriction, law or
         governmental regulation or court decree or order binding on or
         affecting the Borrower; or

                  (c)      result in, or require the creation or imposition of,
         any Lien on any of the Borrower's properties.

         3.2 Government Approval, Regulation, etc. No authorization or approval
or other action by, and no notice to or filing with, any governmental authority
or regulatory body or other Person is required for the due execution, delivery
or performance by the Borrower.

         3.3 Validity, etc. This Amendment constitutes the legal, valid and
binding obligation of the Borrower enforceable in accordance with its terms.

         SECTION 4. MISCELLANEOUS.

         4.1 Continuing Effectiveness, etc. This Amendment shall be deemed to be
an amendment to the Credit Agreement, and the Credit Agreement, as amended
hereby, shall remain in full force and effect and is hereby ratified, approved
and confirmed in each and every respect. After the effectiveness of this
Amendment in accordance with its terms, all references to the Credit Agreement
in the Loan Documents or in any other document, instrument, agreement or writing
shall be deemed to refer to the Credit Agreement as amended hereby.

         4.2 Payment of Costs and Expenses. The Borrower agrees to pay on demand
all reasonable out-of-pocket expenses of the Administrative Agent (including the
fees and out-of-pocket expenses of counsel to the Administrative Agent) in
connection with the negotiation, preparation, execution and delivery of this
Amendment.

         4.3 Severability. Any provision of this Amendment which is prohibited
or unenforceable in any jurisdiction shall, as to such provision and such
jurisdiction, be ineffective to the extent of such prohibition or
unenforceability without invalidating the remaining provisions of this Amendment
or affecting the validity or enforceability of such provision in any other
jurisdiction.

         4.4 Headings. The various headings of this Amendment are inserted for
convenience only and shall not affect the meaning or interpretation of this
Amendment or any provisions hereof.

         4.5 Execution in Counterparts. This Amendment may be executed by the
parties hereto in several counterparts, each of which shall be deemed to be an
original and all of which shall constitute together but one and the same
agreement.

         4.6 Governing Law. THIS AMENDMENT SHALL BE DEEMED TO BE A CONTRACT MADE
UNDER AND GOVERNED BY THE INTERNAL LAWS OF THE STATE OF ILLINOIS.

         4.7 Successors and Assigns. This Amendment shall be binding upon and
shall inure to the benefit of the parties hereto and their respective successors
and assigns.

                                       5
<PAGE>

         IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
executed by their respective officers thereunto duly authorized as of the day
and year first above written.

                                         DELPHI FINANCIAL GROUP, INC.

                                         By /s/ ROBERT M. SMITH, JR.
                                            -------------------------------
                                            Title: Executive Vice President

                                       S-1
<PAGE>

                                         BANK OF AMERICA, N.A., individually and
                                         as Administrative Agent

                                         By /s/  DEBRA BASLER
                                            -------------------------------
                                            Title: Principal

                                       S-2
<PAGE>

                                         WACHOVIA BANK, NATIONAL ASSOCIATION

                                         By /s/  KIMBERLY SHAFFER
                                            -------------------------------
                                            Title: Director

                                       S-3
<PAGE>

                                         FLEET NATIONAL BANK

                                         By /s/  LAWRENCE DAVIS
                                            -------------------------------
                                            Title: Portfolio Manager

                                       S-4
<PAGE>

                                         ING CAPITAL LLC

                                         By /s/ MARK NEWSOME
                                            -------------------------------
                                            Title: Vice President

                                       S-5
<PAGE>

                                         US BANK NATIONAL ASSOCIATION

                                         By /s/  ERIC HARTMAN
                                            -------------------------------
                                            Title: Vice President

                                       S-6
<PAGE>

                                         THE NORTHERN TRUST COMPANY

                                         By /s/ TIMOTHY DUNNING
                                            -------------------------------
                                            Title: Vice President - Credit

                                       S-7