And the LORD said furthermore unto him,
now your hand into your bosom.
And he put his hand into his bosom: and when he took it out, behold, his hand was as leprous as snow.
Read Chapter 4
Ambrose of Milan
Again, another sign which Moses gave points to our Lord Jesus Christ. He put his hand into his bosom and drew it out again, and his hand had become as snow. A second time he put it in and drew it out, and it was again like the appearance of human flesh. This signified first the original glory of the Godhead of the Lord Jesus and then the assumption of our flesh, in which truth all nations and peoples must believe. So he put in his hand, for Christ is the right hand of God; and whosoever does not believe in his Godhead and incarnation is punished as a sinner; like that king who, while not believing open and plain signs, yet afterwards, when punished, prayed that he might find mercy. .
Just as Moses was allowed to perform miracles with a rod, so he was ordered to thrust his hand into his bosom, and when it was brought out again it was found to be leprous; then he was ordered to insert it again, and it was at once healed. This indicates that the Jewish people was to become impure by abandoning the Lord Christ but that it would recover its former health by returning to him.