Purity: Intention (Niyyah) for Performing Ghusl
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 544:
One who gives ghusl to a corpse must have the intention of attaining proximity to Allah the Exalted, and it is sufficient if he has an intention to follow the command of Allah the Exalted.
-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)