What signs did God give Moses to prove that God meant what He said?
God gave Moses two confirming signs: casting his rod to the ground, where it became a serpent, then picking it up as a rod again; and placing his hand in his bosom, where it became leprous, then restoring it whole. These signs proved God meant what He said.
Les explains that God had already used the signs to convince Moses that he indeed was going to be led of God. The first was throwing the rod down, and it became a serpent; picking it up, it again became a rod. The second was placing his hand in his bosom, and it became leprous; taking it out and putting it back, it was whole. These were all signs to prove to Moses that God indeed meant what He said. When Moses continued to debate, saying he was not eloquent and was slow of speech, the Lord asked who made man's mouth and promised to be with his mouth and teach him what to say.