פירוש על שמות 7:10

לתנין means A SERPENT.

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.