He embraced Islam, and the Prophet ﷺ instructed him to perform a full bath with water and lote-tree leaves.
حدثنا عبد الرحمن حدثنا سفيان عن الأغر عن خليفة بن حصين
أنه أسلم فأمره النبي ﷺ أن يغتسل بماء وسدر
Its isnad is sahih. Aghar is Ibn Sabbah Tamimi Minqari, considered trustworthy by them, and his hadith appears in the Sunan. Khalifa bin Husayn bin Qays bin Asim is a trustworthy, well-known Quran reciter. The hadith was narrated by Abu Dawud, 1/97, no. 355, and Tirmidhi graded it hasan, 2/503, no. 605, and Nasai, 1/109, all of them in the chapter on Purification, on the man who embraces Islam and then performs ghusl.