Or HaChaim on Exodus 7:6/אור החיים על שמות ז׳:ו׳

1 ויעש משה ואהרון…כן עשו, Moses and Aaron did (as G'd had commanded)..so they did. Why does this verse mention twice that Moses and Aaron did what G'd had commanded them to do? The Torah may be telling us that Moses and Aaron carried out their mission on two levels. 1) The carried out all those instructions of G'd that made sense to them. 2) They tried to understand G'd's purpose in every detail of the instructions they received. By not deviating in a single detail from the instructions they had received, Moses and Aaron proved that their only concern was to carry out G'd's intention to the letter.

2The Torah may also testify here that Moses and Aaron had no ulterior motives in carrying out any details of G'd's instructions. We find a parallel to this in Deut. 6,25 where the Torah states that carrying out G'd's laws will be considered צדקה, righteousness for us, if we perform them כאשר צונו, "as He has commanded us." It is not enough to merely carry out G'd's instructions, but in order to qualify for praise one must carry them out precisely as He commanded us. In our verse the Torah testifies that this is what Moses and Aaron did.

3Another point that our verse wanted to mention is that both Moses and Aaron did not miss any opportunity to mention G'd every time they did anything. The Torah underlines the word עשו to show that Moses and Aaron carried out G'd's instructions immediately after they had received them.