But, if the oath of God to Abraham is to inspire us with new courage, we must resemble Abraham in the eager earnestness and calm endurance of his faith. The passage has often been treated as if the oath had been intended to meet the weakness of faith. But unbelief is logician enough to argue that God's word is as good as His bond; yea, that we have no knowledge of His oath except from His word. The Apostle refers to the greatest instance of faith ever shown even by Abraham, when he withheld not his son, his beloved son, on Moriah. The oath was made to him by God, not before he gave up Isaac, in order to encourage his weakness, but when he had done it, as a reward of his strength. Philo's fine sentence, which indeed the sacred writer partly borrows, is intended to teach the same lesson: that, while disappointments are heaped on sense, an endless abundance of good things has been given to the earnest soul and the perfect man.[112] It is to Abraham when he has achieved his supreme victory of faith that God vouchsafes to make oath that He will fulfil His promise. This gives us the clue to the purport of the words. Up to this final test of Abraham's faith God's promise is, so to speak, conditional. It will be fulfilled if Abraham will believe. Now at length the promise is given unconditionally. Abraham has gone triumphantly through every trial. He has not withheld his son. So great is his faith that God can now confirm His promise with a positive declaration, which transforms a promise made to a man into a prediction that binds Himself. Or shall we retract the expression that the promise is now given unconditionally? The condition is transferred from the faith of Abraham to the faithfulness of God. In this lies the oath. God pledges His own existence on the fulfilment of His promise. He says no longer, "If thou canst believe," but "As true as I live." Speaking humanly, unbelief on the part of Abraham would have made the promise of God of none effect; for it was conditional on Abraham's faith. But the oath has raised the promise above being affected by the unbelief of some, and itself includes the faith of some. St. Paul can now ask, "What if some did not believe? Shall their unbelief make the _faith_" (no longer merely the promise) "of God without effect?"[113] Our author also can speak of two immutable things, in which it was impossible for God to lie. The one is the promise, the immutability of which means only that God, on His part, does not retract, but casts on men the blame if the promise is not fulfilled. The other is the oath, in which God takes the matter into His own hands and puts the certainty of His fulfilling the promise to rest on His own eternal being.
The Apostle is careful to point out the wide and essential difference between the oath of God and the oaths of men. "For men swear by the greater;" that is, they call upon God, as the Almighty, to destroy them if they are uttering what is false. They imprecate a curse upon themselves. If they have sworn to a falsehood, and if the imprecation falls on their heads, they perish, and the matter ends. And yet an oath decides all disputes between man and man.[114] Though they appeal to an Omnipotence that often turns a deaf ear to their prayer against themselves; though, if the Almighty were to fling retribution on them, the wheels of nature would whirl as merrily as before; though, if their false swearing were to cause the heavens to fall, the men would still exist and continue to be men;--yet, for all this, they accept an oath as final settlement. They are compelled to come to terms; for they are at their wits' end. But it is very different with the oath of God. When He swears by Himself, He appeals, not to His omnipotence, but to His truthfulness. If any jot or tittle of God's promise fails to the feeblest child that trusts Him, God ceases to be. He has been annihilated, not by an act of power, but by a lie.