John Chrysostom : And in another way; Having said that He is on high, he affirms and proves that He is a Priest from every consideration, from Melchisedec, from the oath, from offering sacrifice. From this he also frames another and necessary syllogism. "For if" (he says) "He had been on earth, He would not be a Priest, seeing that there are priests who offer the gifts according to the Law." If then He is a Priest (as He really is), we must seek some other place for Him. "For if He were" indeed "on earth, He should not be a priest." For how could He be? He offered no sacrifice, He ministered not in the Priest's office. And with good reason, for there were the priests. Moreover he shows, that it was impossible that He should be a priest upon earth. For how could He be? There was no rising up against the appointed Priests, he means. — Homily on Hebrews 14 Oecumenius : "For if he were on earth." This was the case, if he had not died, nor had he been taken up after rising. "he would not be a priest at all." For there would be others, even a rebellion would be present. But now he has died, so that he may offer the sacrifice. Rising from the dead, he was taken up, so that he might have a place in heaven, where he must serve as a priest. To serve as a priest means to intercede for us. All these humble words were said, both because of humanity and because of the childishness of those who hear. — The Pseudo-Oecumenian Catena on Hebrews Theodoret of Cyrus : He mentioned this by way of defense to stress that he was not criticizing the law but regarding it also as venerable for containing the type of the heavenly things. This was the reason he said it was pointless to refer to him as a priest while living on earth, there being priests according to the law discharging the worship prescribed by the law. So if the priesthood according to the law also came to an end, and the high priest according to the order of Melchizedek offered sacrifice and made further sacrifices unnecessary, why do the priests of the New Covenant perform the sacramental liturgy? It is clear to those versed in divine things, however, that it is not another sacrifice we offer; rather, we perform the commemoration of the one, saving sacrifice. The Lord himself, remember, required this of us, "Do this in memory of me," so that we should recall with insight the type of the sufferings undergone for us, kindle love for the benefactor and look forward to the enjoyment of the good things to come. — INTERPRETATION OF Hebrews 8