Well, when people go on a journey to a special place called Mecca for Hajj, they are supposed to follow certain rules. One of these rules is that they are not allowed to be friends with or hang out with people who believe in many gods (polytheists).
If someone accidentally becomes friends with a polytheist during their Hajj journey, they have to tell everyone that they don't really want to be friends with that person anymore. They have to "disavow" them, which means saying they don't agree with their beliefs anymore.
This is important because Hajj is a very special journey where people try to become closer to God and show their faith. Being friends with someone who believes in many gods could make God not happy with them, so they have to be careful.