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 6356
Ibn Umar reported Allah's Messenger (may peace be upon him) as saying: Gabriel impressed upon me (the kind treatment) towards the neighbour (so much) that I thought as if he would soon confer upon him the (right) of inheritance.