Is it obligatory to perform the full ritual bath for one who wishes to convert to Islam?

Question:
The fact that he (i.e., Thumamah) performed the full ritual bath on his own before converting indicates that the full ritual bath is not obligatory?

Answer:
Yes, this is one of the proofs that it is not obligatory; because the Messenger of Allah (peace and blessings be upon him) did not order him to do so. He went and did it himself, and after he converted, the Messenger of Allah (peace and blessings be upon him) did not say to him, "Perform the full ritual bath."