A.T. Robertson Commentary Hebrews 7:21

"(for they indeed have been made priests without an oath; but he with an oath by him that saith of him, The Lord sware and will not repent himself, Thou art a priest for ever);" — Hebrews 7:21 (ASV)

Have been made (εισιν γεγονοτες). Periphrastic perfect active indicative of γινομα (perfect active participle of γινομα) and then εισιν. The parenthesis runs from ο μεν γαρ (for they) to εις τον αιωνα (for ever, end of verse 21).

But he with an oath (ο δε μετα ορκωμοσιας). Positive statement in place of the negative one in verse 20.