Purity: Qualifications of the Person Performing Ghusl

Practical Laws of Islam as per the teachings of Ayatullah Sistani

Ruling 543:

One who gives ghusl to a corpse must be sane, Muslim, and, based on obligatory precaution, a Twelver Shia; furthermore, he must know the rulings of ghusl. If a mumayyiz child performs ghusl correctly, it is acceptable [for him to perform the ghusl]. In the event that the deceased is not a Twelver Shia and someone from the deceased’s religious denomination (madhhab) gives him ghusl – albeit according to the laws of his denomination – the responsibility is lifted from Twelver believers unless a Twelver believer is the guardian of the deceased, in which case the responsibility is not lifted from him.

-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)