This is usually done by reinforcing the witness's concept of divine punishment for false swearing. If the witness objects to taking an oath, a solemn affirmation may be taken instead. The obligation of an oath or affirmation is regarded as completely binding on the witness's conscience.
Oaths vary in different countries according to different laws, constitutions, and religious beliefs.
It is the common law of England that the form of an oath accommodate the religion of the swearer. A Christian may take an oath on the Bible, a Jew may be sworn on the Pentateuch or the Old Testament, a Muslim may be sworn on the Koran and so forth. No special form of swearing is necessary if the witness does not have a religion. The simple principle of the common law is that oaths should be administered according to the person's opinion and conscience. Witnesses must be allowed to choose the oath they regard as binding and must not be coerced into using any particular one.