Sahih Muslim Book 1, Hadith Number 139.

Chapter : The love of Ansar (helpers) and ‘All (may Allah be pleased with all of them) is (an Ingredient) of Iman and (one of) its signs, and hatred against them is a sign of dissemblance.

It is reported on the authority of Abu Huraira that the Messenger of Allah (may peace and blessings be upon him) said: A person who believes in Allah and the Last Day never nurses a grudge against the Ansar.