John Gill Commentary Exodus 7:6

"And Moses and Aaron did so; as Jehovah commanded them, so did they." — Exodus 7:6 (ASV)

And Moses and Aaron did as the Lord commanded them
After this they never showed any reluctance, or made any objection to any message they were sent with, or any work they were ordered to do, but went about it at once, and performed it with all readiness and cheerfulness:

so did they ;
which is not a superfluous and redundant expression, but very emphatic, showing with what care and diligence they did every thing, and how exactly they conformed in all things to the divine will.