21 For in the power of the Holy Ghost, by the will of Father and Son, Peter stood with the Eleven, and lifting up his voice, (according to the text, Lift up your voice with strength, you that bringest good tidings to Jerusalem), captured in the spiritual net of his words, about three thousand souls. So great was the grace which wrought in all the Apostles together, that, out of the Jews, those crucifiers of Christ, this great number believed, and were baptized in the Name of Christ, and continued steadfastly in the Apostles' doctrine and in the prayers. And again in the same power of the Holy Ghost, Peter and John went up into the Temple at the hour of prayer, which was the ninth hour, and in the Name of Jesus healed the man at the Beautiful gate, who had been lame from his mother's womb for forty years; that it might be fulfilled which was spoken, Then shall the lame man leap as an hart. And thus, as they captured in the spiritual net of their doctrine five thousand believers at once, so they confuted the misguided rulers of the people and chief priests, and that, not through their own wisdom, for they were unlearned and ignorant men, but through the mighty power of the Holy Ghost; for it is written, Then Peter filled with the Holy Ghost said to them. So great also was the grace of the Holy Ghost, which wrought by means of the Twelve Apostles in them who believed, that they were of one heart and of one soul, and their enjoyment of their goods was common, the possessors piously offering the prices of their possessions, and no one among them wanting anything; while Ananias and Sapphira, who attempted to lie to the Holy Ghost, underwent their befitting punishment.
Source: Catechetical Lectures (New Advent)