Complex sentence: He was private about his beliefs and respected the beliefs of Christian belief, several people who knew him personally, such as Chaplain of the Senate Phineas Gurley and Mary Todd Lincoln herself, stated that he believed in Christ in the religious sense.
Split into simpler sentences: He was private about his beliefs and respected the beliefs of others. Although Lincoln never made an unambiguous public profession of Christian belief, several people who knew him personally, such as Chaplain of the Senate Phineas Gurley and Mary Todd Lincoln herself, stated that he believed in Christ in the religious sense.