Tafsir of Ta-Ha 20:21

When he saw that wondrous and terrifying matter, he was seized by such fear and aversion as humans are seized by when facing horrors and terrors.

Ibn Abbas said: It transformed into a male serpent that swallowed rocks and trees. When he saw it swallowing everything, he feared it and recoiled. Others said: He only feared it because he knew what Adam had encountered from it. It is said: When his Lord said to him, "Do not fear," his fear vanished and his soul became so tranquil that he placed his hand into its mouth and took hold of its jaws.

"Sīratahā" (its former state): Derived from sayr (to travel/conduct), like rukba (a manner of riding) is from rukūb. It is said, "So-and-so conducted himself (sāra) in a good manner (sīra)." Then, the usage expanded to mean a path or method.

It is also said to mean "the way of the ancients." It may be an adverbial accusative, meaning: "We will return it to its first way," i.e., to the state it was in when it was a staff.

It may also be derived from ‘āda (to return), in the sense of "returning to it." From this is the verse of Zuhayr: "And it returns to you to meet it..."—in which case it takes two objects.

A third, excellent interpretation is that "We will return it" is independent and not connected to "its former state." It means: It was created initially as a staff, then that state ceased when it transformed into a living creature; so, after its transformation, We will return it to how We created it at first. In this case, sīratahā is in the accusative due to an implied verb, meaning: "It will proceed in its first manner," i.e., We will return it to proceeding in its first manner, where you would lean upon it and have the needs met by it that you have known.