Why did God give Moses the signs of the rod and the leprous hand?
God gave Moses the rod and leprous-hand signs so Israel would believe that the God of Abraham, Isaac, and Jacob had appeared to him and that he was God's man. These miraculous signs authenticated Moses' commission before the enslaved people in Egypt, confirming his divine appointment.
Les explains that when God sent Moses back to the people under slavery in Egypt, He said that if they did not believe him, he should throw the rod on the ground, and it would become a serpent; then he should pick it up, and it would become his rod. God also gave another sign: Moses put his hand in, and it became leprous; when he took it out, it was perfectly whole again. These signs were given to Moses to prove to Israel that he was God's man. The stated purpose was that they may believe that the God of their fathers, the God of Abraham, Isaac, and Jacob, had appeared unto him.