Or HaChaim on Exodus 7:10/אור החיים על שמות ז׳:י׳

1 ויעשו כן כאשר צוה, They did as G'd had commanded, etc. The reason the Torah writes the words כן כאשר, i.e. repeating basically the same word is, because it tells us that Moses and Aaron a) did what G'd had told them to, b) did not do so until Pharaoh had requested the miracle from them.

2The Torah also wanted us to know that though anyone who performs miracles immediately raises his own image in the eyes of the onlookers, Moses and Aaron had no such considerations. They did what they did only at the behest of G'd. It is the mark of the truly righteous not to perform their own will but to perform what they perceive to be G'd's will.