Spake out boldly (parrēsiasamenoi). First aorist middle participle of parrēsiazomai, to use freedom in speaking, to assume boldness. Both Paul and Barnabas accepted the challenge of the rabbis. They would leave their synagogue, but not without a word of explanation.
It was necessary to you first (Humin ēn anagkaion prōton). They had done their duty and had followed the command of Jesus (Act 1:8). They use the very language of Peter in Act 3:26 (humin prōton) “to you first.” This position Paul as the apostle to the Gentiles will always hold, the Jew first in privilege and penalty (Rom 1:16; Rom 2:9, Rom 2:10).
Ye thrust it from you (apōtheisthe auton). Present middle (indirect, from yourselves) indicative of apōtheō, to push from. Vigorous verb seen already in Act 7:27, Act 7:39 which see.
Judge yourselves unworthy (ouk axious krinete heautous). Present active indicative of the common verb krinō, to judge or decide with the reflexive pronoun expressed. Literally, Do not judge yourselves worthy. By their action and their words they had taken a violent and definite stand.
Lo, we turn to the Gentiles (idou strephometha eis ta ethnē). It is a crisis (idou, lo): “Lo, we turn ourselves to the Gentiles.” Probably also aoristic present, we now turn (Robertson, Grammar, pp. 864-70). Strephometha is probably the direct middle (Robertson, Grammar, pp. 806-08) though the aorist passive estraphēn is so used also (Act 7:39). It is a dramatic moment as Paul and Barnabas turn from the Jews to the Gentiles, a prophecy of the future history of Christianity. In Romans 9-11 Paul will discuss at length the rejection of Christ by the Jews and the calling of the Gentiles to be the real (the spiritual) Israel.