Tafsir of Ta-Ha 20:20

He cast it down, and behold! It was a snake, moving quickly. This means that the stick changed into a huge snake, like a long python, and it moved with rapid movements. It moved as if it were the fastest type of small snake. Yet, it was in the form of the largest snake, while still having the fastest of movements

تسعى

(moving quickly), moving restlessly. Then Allah said,