A.T. Robertson Commentary Acts 2:39

"For to you is the promise, and to your children, and to all that are afar off, [even] as many as the Lord our God shall call unto him." — Acts 2:39 (ASV)

The promise (η επαγγελια). The promise made by Jesus (1:4) and foretold by Joel (verse 18).

To you (υμιν). You Jews. To your descendants, sons and daughters of verse 17.To all that are afar off (πασιν τοις εις μακραν. The horizon widens and includes the Gentiles. Those "afar off" from the Jews were the heathen (Isaiah 49:1; 57:19; Ephesians 2:13,17). The rabbis so used it.

Shall call (αν προσκαλεσητα). First aorist middle subjunctive with αν in an indefinite relative clause, a perfectly regular construction. The Lord God calls men of every nation anywhere whether Jews or Gentiles. It may be doubted how clearly Peter grasped the significance of these words for he will have trouble over this very matter on the housetop in Joppa and in Caesarea, but he will see before long the full sweep of the great truth that he here proclaims under the impulse of the Holy Spirit. It was a great moment that Peter here reaches.