Peter saw the crowd staring at him and John as if the two of them had done the miracle. His two questions turn their eyes away from the apostles. The first asks why they marvel at all; the second asks why they look at the apostles as the source. Barnes explains that Peter was not faulting their wonder, "for that was proper," but the fact "that they looked on himself and John as if they had been the authors of this healing." Gill says Peter was suggesting that they ought to look to God and to the Lord Jesus Christ instead. Matthew Henry notes that Peter and John "would not take the honour of this miracle to themselves, but carefully transmitted it to Christ."

Peter answers his own questions in the sermon that follows. It was not the apostles but "the God of Abraham, and of Isaac, and of Jacob" who "hath glorified his Son Jesus" (Acts 3:13). The man was healed by Jesus' name: "his name through faith in his name hath made this man strong" (Acts 3:16). Peter then tells the crowd they had denied "the Holy One and the Just" and killed "the Prince of life, whom God hath raised from the dead" (Acts 3:14-15), and he calls them to "Repent ye therefore, and be converted" (Acts 3:19).

Solomon's porch was a covered walkway along the east side of the temple court, which Barnes describes as notable for its magnificence. The Greek word behind "look ye so earnestly" is atenizo, which Thayer defines "to fix the eyes on, gaze upon." It is the same word used when Peter, "fastening his eyes upon him," first looked at the lame man (Acts 3:4). Now the crowd fixed its eyes on Peter.

The word translated "holiness" is eusebeia, meaning godliness or piety (the ESV has "piety"). Barnes explains Peter's denial: they had not healed him by any art of healing or medicine (power), nor had God rewarded their own "personal and eminent piety" (holiness).

This question protects the glory of God. A miracle had drawn a huge crowd, and it would have been easy to let people think the apostles were special. Barnes observes that here was ample opportunity for the apostles to build a reputation of their own, but they refused all such personal honor and ascribed everything to the Lord Jesus. Peter used the crowd's amazement to point them to the One they had rejected (Acts 3:13-15).

The healing was a sign about Jesus, not about Peter. Peter had said at the gate, "In the name of Jesus Christ of Nazareth rise up and walk" (Acts 3:6), and he says the same thing to the crowd (Acts 3:16). The God who healed the man is the God who raised Jesus from the dead, and Peter calls the crowd to repent "that your sins may be blotted out" (Acts 3:15, 19).