Messiah's Priesthood

For by this statement, "The Lord has sworn, and will not repent: You are a priest for ever, after the order of Melchizedek," with an oath God has shown Him (on account of your unbelief) to be the High Priest after the order of Melchizedek; i.e., as Melchizedek was described by Moses as the priest of the Most High, and he was a priest of those who were in uncircumcision, and blessed the circumcised Abraham who brought him tithes, so God has shown that His everlasting Priest, called also by the Holy Spirit Lord, would be Priest of those in uncircumcision.  Those too in circumcision who approach Him, that is, believing Him and seeking blessings from Him, He will both receive and bless.  And that He shall be first humble as a man, and then exalted, these words at the end of the Psalm show: "He shall drink of the brook in the way," and then, "Therefore shall He lift up the head."

Justin Martyr, Dialogue with Trypho, 33