Is there any evidence that an unbeliever (kafir) is not required to perform ghusl (ritual bathing) if he embraces Islam, and if not, how should he be treated Islamically?

Contemporary Sufi orders contain deviations that may amount to polytheism (shirk), but deeming someone an infidel (takfir) and judging them apostate (riddah) is dangerous and requires Islamic legal controls and well-grounded scholars. If a person's apostasy is proven and then they repent, upon their mere embrace of Islam, the rulings of apostasy are lifted from them, and they are entitled to the rights of a Muslim.

Regarding the ruling on their ritual bathing (ghusl) upon embracing Islam: The Malikis and Hanbalis are of the opinion that it is obligatory, citing prophetic traditions, including the Prophet's (peace be upon him) command to Thumamah ibn Uthal and Qays ibn Asim to perform ghusl upon their conversion to Islam. The Hanafis and Shafi'is, however, hold that it is recommended due to the lack of widely transmitted narrations ordering it. The more preponderant opinion is the obligation of ghusl.

Therefore, one should gently inform converts of the obligation of ghusl, unless there is a concern of causing a greater harm.