Albert Barnes Commentary Acts 4:22

"For the man was more than forty years old, on whom this miracle of healing was wrought." — Acts 4:22 (ASV)

For the man, etc. The age of the man is mentioned to show the certainty and greatness of the miracle. If it had been a man who had been lame only a few years, or if it had been a child or a very young man, the case would not have been so remarkable. But, after a continuance of forty years, all hope of healing him by any ordinary means must have been abandoned; and all pretense that this was trickery or deception must have been absurd.