Sahih Muslim Book 32, Hadith Number 6220.

Chapter : It is forbidden to populate atrocity upon a Muslim, to humiliate him, to insult him, and inviolable is his blood, honour and wealth.

This hadith has been transmitted on the authority of Abu Huraira with some addition (and it is this): “Verily Allah does not look to your bodies nor to your faces but He looks to your hearts,” and he pointed towards the heart with his fingers.