John Gill Commentary Exodus 4:30

"and Aaron spake all the words which Jehovah had spoken unto Moses, and did the signs in the sight of the people." — Exodus 4:30 (ASV)

And Aaron spoke all the words which the Lord had spoken to
Moses
As Moses had related to him, being his mouth and spokesman:

and did the signs in the sight of the people ;
not Aaron, but Moses, and these were the turning of his rod into a serpent, and the serpent into a rod again; putting his hand into and out of his bosom, when it was leprous, and then doing the same when it was well again; and taking water out of the river, and changing it into blood, which he did for the confirmation of his mission.