What does Acts 4:22 mean?

Although Peter and John are devout Jesus-followers, they are also devout Jews. Jesus was a Jew, and belief in Him is the fulfillment of the ceremonies and requirements of Judaism. So it is not unusual that they went to the temple for afternoon prayers. While entering the gate, they saw a beggar who has been lame since birth. They had no money, but they do have the power of the Holy Spirit, so they healed him. When the by-standers realize what they've done, they crowd around them. Peter and John explain they performed the miracle through the name and authority of Jesus of Nazareth, whom their audience had crucified. Hundreds confess and become Jesus-followers (Acts 3:1–26; 4:4).

The Sanhedrin is unhappy, both with Peter and John's popularity (Acts 5:17) and with the men's insistence that resurrection from the dead is true (Acts 4:2). They arrest the two disciples and demand to know more. Peter reiterates that they healed by the power of Jesus, who has risen from the dead. The Sanhedrin has no choice but to release them. It is not illegal to teach that there is an afterlife—the Pharisees do—and it's very obvious the healing of the lame man is a legitimate miracle.

The man's age is not particularly significant, but the man's age in conjunction with the fact that he was born lame is (Acts 3:2). He has been lame for more than forty years. There is no earthly way at this point that he could spontaneously heal through natural means. It's no wonder the crowd listened to the message given by such miracle workers.