The Book of Virtue, Good Manners and Joining of the Ties of Relationship (Kitab Al-Birr was-Salat-I-wa'l-Adab)
Muslim :: Book 32 : Hadith 6220
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.