Adam Clarke on Acts 2:39

For the promise is unto you - Jews of the land of Judea: not only the fulfillment of the promise which he had lately recited from the prophecy of Joel was made to them, but in this promise was also included the purification from sin, with every gift and grace of the Holy Spirit.

To all that are afar off - To the Jews wherever dispersed, and to all the Gentile nations; for, though St. Peter had not as yet a formal knowledge of the calling of the Gentiles, yet, the Spirit of God, by which he spoke, had undoubtedly this in view; and therefore the words are added, even as many as the Lord our God shall call, i.e. all to whom, in the course of his providence and grace, he shall send the preaching of Christ crucified.