So God, willing more abundantly to show unto the heirs of promise the immutability of his counsel, confirmed it by an oath:
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John Chrysostom
AD 407
God, however, ought to have been believed even without an oath: Hebrews 6:17 wherein (he says) God willing more abundantly to show unto the heirs of promise the immutability of His counsel, confirmed it [lit. mediated ] by an oath. In these words he comprehends also the believers, and therefore mentions this promise which was made to us in common [with them]. He mediated (he says) by an oath. Here again he says that the Son was mediator between men and God.