Then Jesus said to the man, “Stretch out your hand.” So he stretched it out, and it was restored to full use, just like the other.
The Jewish teachers had corrupted many of the commandments, by interpreting them more loosely than they were intended; a mistake which Christ discovered and rectified (ch. 5) in his sermon on the mount: but concerning the fourth commandment, they had erred in the other extreme, and interpreted it too strictly.
Commenting on Matthew 12:1-13
Then the Pharisees went out,.... Of the synagogue, being, as Luke says, filled with madness, at the unanswerableness of his arguments; and because of the violation of the sabbath, as they thought; and most of all, because of the miracle wrought by him; and which was so glaringly a proof of his being Lord of the sabbath, and could not fail of creating him esteem...
Verse 13. And he said, Stretch forth thine hand. This was a remarkable commandment. The man might have said that he had no strength; that it was a thing which he could not do. Yet, being commanded, it was his duty to obey. He did so, and was healed. So the sinner; it is his duty to obey whatever God commands.