A.T. Robertson Commentary Hebrews 7:28

"For the law appointeth men high priests, having infirmity; but the word of the oath, which was after the law, [appointeth] a Son, perfected for evermore." — Hebrews 7:28 (ASV)

After the law (μετα τον νομον). As shown in verses 11-19, and with an oath (Psalms 110:4).

Son (υιον). As in Ps 2:7; Hebrews 1:2 linked with Ps 110:4.

Perfected (τετελειωμενον). Perfect passive participle of τελειοω. The process (2:10) was now complete. Imperfect and sinful as we are we demand a permanent high priest who is sinless and perfectly equipped by divine appointment and human experience (2:17f.; 5:1-10) to meet our needs, and with the perfect offering of himself as sacrifice.