For the (a) promise is unto you, and to your children, and to all that are afar off, [even] as many as the Lord our God shall call.
(a) The word that is used here shows us that it was a free gift.
Related Commentaries of Acts 2:39
Acts 2:39
39 For the promise is unto you, and to your children, and to all that are afar off, even as many as the Lord our God shall call.