Albert Barnes on Acts 3:7

And he took him. He took hold of his hand. To take hold of the hand in such a case was an offer of aid, an indication that Peter was sincere, and was an inducement to him to make an effort. This may be employed as a beautiful illustration of the manner of God when he commands men to repent and believe, He does not leave them alone; he extends help, and aids their efforts. If they tremble, and feel that they are weak, and needy, and helpless, his hand is stretched out, and his power exerted to impart strength and grace.

His feet and ancle bones. The fact that strength was immediately imparted; that the feet, long lame, were now made strong, was a full and clear proof of miraculous power.