My father, may Allah سبحانه وتعالى be pleased with him, stated in his letter to me: Know, O my son, that the ruling concerning all claims is that the burden of proof (evidence) lies upon the claimant, and the oath is upon the defendant. If the defendant refuses to take the oath, the right (claim) becomes binding upon him. If the defendant refers the oath back to the claimant, in cases where the claimant does not have two witnesses, and the claimant refuses to swear, then he has no right to the claim. However, in cases involving hudud (prescribed punishments), there is no oath, and in cases involving bloodshed (murder or bodily harm), the burden of proof lies upon the defendant, while the oath is upon the claimant-so that the life of a Muslim is not lost without justice.
Commentary #1