Purity: Ruling on Purity Based on Statement of Appointed Washer
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 222
If a person who has been appointed to wash someone’s clothes says that he has washed them and one is confident of the truthfulness of what he says, then those clothes are pure.
-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)