Apostolic Constitutions : Whence also the prophet says, The Lord hath sworn, and will not repent: Thou art a priest for ever, after the order of Melchizedec. — CONSTITUTIONS OF THE HOLY APOSTLES Hippolytus of Rome : For also our Father, on beholding the Good One, and on being initiated with Him, preserved the mysteries respecting which silence is enjoined, and sware, as it has been written, "The Lord sware, and will not repent." Having, then, in this way set the seal to these tenets, he seeks to inveigle (his followers) with more legends, (which are detailed) through a greater number of books; and so he conducts (his readers) to the Good One, consummating the initiated (by admitting them into) the unspeakable Mysteries. ... And this oath, (Justinus) says, our Father Elohim sware when He was beside the Good One, and having sworn He did not repent (of the oath), respecting which, he says, it has been written, "The Lord sware, and will not repent." Now the oath is couched in these terms: "I swear by that Good One who is above all, to guard these mysteries, and to divulge them to no one, and not to relapse from the Good One to the creature." — Hippolytus Refutation of All Heresies Book V John Chrysostom : "And inasmuch as not without an oath." What is "And inasmuch as not without an oath"? That is, Behold another difference also. And these things were not merely promised (he says). "For those priests were made without an oath, but This with an oath, by Him that said unto Him, The Lord swore and will not repent, Thou art Priest for ever after the order of Melchisedec. By so much was Jesus made a surety of a better covenant." He lays down two points of difference, that it hath no end as the covenant of the Law had; and this he proves from its being Christ who exercises the priesthood; for he says "according to the power of an endless life." And he proves it also from the oath, because "He swore," and from the fact; for if the other was cast out, because it was weak, this stands firm, because it is powerful. He proves it also from the priest. How? Because He is One only; and there would not have been One only, unless He had been immortal. For as there were many priests, because they were mortal, so here is The One, because He is immortal. "By so much was Jesus made a surety of a better covenant," inasmuch as He swore to Him that He should always be Priest; which He would not have done, if He were not living. — Homily on Hebrews 13 Oecumenius : "For they indeed became priests without an oath." Then, from the lesser, the comparisons of the priests among the Jews and our High Priest.For the legal priests, he says, were made priests without an oath; for God never found it necessary to swear: "You shall be a priest according to the law." But Christ, with an oath, made by the one who said to Him, as it were, by God; for God spoke through David: "You are a priest," in a certain new way; for He is not according to Aaron, but according to Melchizedek. — The Pseudo-Oecumenian Catena on Hebrews