Brethren (andres adelphoi). Literally, men, brethren or brother men. More dignified and respectful than just “brethren.” Demosthenes sometimes said Andres Athēnaioi. Cf. our “gentlemen and fellow-citizens.” Women are included in this address though andres refers only to men.
It was needful (edei). Imperfect tense of the impersonal dei with the infinitive clause (first aorist passive) and the accusative of general reference as a loose subject. Peter here assumes that Jesus is the Messiah and finds scripture illustrative of the treachery of Judas. He applies it to Judas and quotes the two passages in Act 1:20 (Psa 69:25; Psa 109:8). The Holy Spirit has not yet come upon them, but Peter feels moved to interpret the situation. He feels that his mind is opened by Jesus (Luk 24:45). It is a logical, not a moral, necessity that Peter points out. Peter here claims the Holy Spirit as speaking in the scriptures as he does in 2Pe 1:21. His description of Judas as “guide” (hodēgou) to those who seized (sullabousin) Jesus is that of the base traitor that he was. This very verb occurs in Luk 22:54 of the arrest of Jesus.