Why does the Torah write that Aharon's staff swallowed those of magicians and not that the snake swallowed them?
Rashi: Because it was only after the snakes turned back into staffs that Aharon's staff swallowed theirs. 1
Hadar Zekenim: This was an additional miracle. Also, it did not become thicker after swallowing them. Pharaoh feared, what if it will swallow me and my throne?!
Presumably, the Pasuk refers to the staff of Aharon, because strictly speaking, it was not the snake that belonged to Aharon but the staff (turned snake).