Hebrews 6:16

For men swear by the greater; and in every dispute of theirs the oath is final for confirmation.

This appeal to the custom of people in requiring judicial oaths, even making it the reason for God's doing so, would appear to give the most positive assurance that the taking of such oaths is not to be considered sinful. If so, our Saviour's command to "swear not at all" (Matthew 4:34) could be understood as making an exception of the type of oath considered here; but this is far from certain. Even if the judicial oath should be allowed as an exception, Christ's command still stands opposed to the vast majority of oaths which people continually swear, most of them utterly needless, and many of them profane as well as needless. The Christian community through the ages, out of regard to Christ's word, have elected to "affirm" or "testify under the penalties of perjury"; and such is a safe course of action and one generally allowed by enlightened courts which take into account the requirement of absolute honesty in all their declarations, Christians being under a much stricter rule than that of any earthly court.

On the reasons for God's doing such a thing as "swearing," see under Hebrews 4:10. The probable reason why the author of Hebrews stressed God's oath to Abraham at this place was that he had the purpose of comparing it, a little later, with another oath God took regarding the "priest forever after the order of Melchizedek." Such a comparison would be calculated to bear the greatest weight with Hebrew Christians. The matter of God's oath would show that the Messiah's being the antitype of Melchizedek was not a side issue at all but was on a parity with election of the chosen people themselves.