Once there was some rift between Muhajireen and Ansar sahaba. One person got up and said, YA LAL-ANSAAR.. O Ansaar!! The other sahabi called ya lal muhajireen. O muhajireen.. Rasool Allah heard it. He came with a red face (in anger) and said STOP THIS! THIS (racism) is Rotten! Racism is very difficult to remove. Its a branch of Hubb e Jaah and Pride.