New Defender's Study Bible Notes
1:20 book of Psalms. The reference is to Psalm 69:25, which contains several other prophetic references to the future sufferings of Messiah (Psalm 69:8-9,21).
1:20 bishoprick. The last clause is a free quote from Psalm 109:8. The word “bishoprick” literally means “overseer” and should be read here as “office.” Judas and his responsibilities needed to be assumed by another qualified disciple.
1:22 witness with us. Another requirement for being a member of the twelve apostles was that he must have witnessed the resurrected Christ. Note also I Corinthians 9:1.