Mar 9:38 John said to Jesus, “Teacher, we saw someone using Your name to cast out demons, but we told him to stop because he wasn’t in our group.”
Mar 9:39 “Don’t stop him!” Jesus said. “No one who performs a miracle in My name will soon be able to speak evil of Me.
Mar 9:40 Anyone who is not against us is for us.
That's what MORMONs rely upon.