Reference: al-Bid’u wal-Muhdathaat wa maa laa asla lahu – Page 404
Question: What is the ruling regarding washing the stones for stoning [the Jamaraat]?
Response: They should not be washed. Rather, if a person washes them with the intention of worshiping Allaah [by this action], then this is an innovation because the Prophet (sal-Allaahu ‘alayhi wa sallam) did not do this.