God's condescension in confirming promises by oath.
It is a weakness on the part of man to need any confirmation of a promise which God makes. "God cannot lie" (Titus 2:1-15:18); "He keepeth his promise forever" (Psalms 146:6). When he condescends to swear that his promise shall hold good, it does not really add to the certainty of the thing promised, since the certainty was absolute from the first. But man is so accustomed to misdoubt his fellows that he will even misdoubt God, as though with him were "variableness or shadow of turning." And God, knowing man's heart and compassionating his weakness, does sometimes, though but rarely, add to his promises, for man's greater contentment, the confirmation of an oath. After the Flood God covenanted with mankind that he would never again destroy the earth by water (Genesis 9:11), and confirmed the covenant by oath (Isaiah 65:9). On the call of Abraham, he swore that he would give the land of Canaan to his posterity (Genesis 24:7), and afterwards that in his seed should all the nations of the earth be blessed. With David he made a covenant, and swore to it, that he would "establish his seed forever, and build up his throne to all generations" (Psalms 89:3, Psalms 89:4). To his own Son he swore, at what time we know not, "Thou art a Priest forever, after the order of Melchizedek" (Psalms 110:4). And here we find that he condescended to swear to Israel that the Assyrians should "be broken," and their yoke "depart off them." Wonderful condescension of him whose word is truth! Not merely not to punish those who doubt him, but to compassionate them, to make allowance for them, to yield compliance to their weakness, and give them such an assurance as compels their belief. "God, willing more abundantly to show unto the heirs of promise the immutability of his counsel, confirmed it by an oath, that by two immutable things, in which it was impossible for God to lie, they might have a strong consolation"—a hope on which to anchor their soul (Hebrews 6:17-19).