Sahih Muslim
The Book of Virtue, Good Manners and Joining of the Ties of Relationship (Kitab Al-Birr was-Salat-I-wal-Adab)
Book Number: 032 / Hadith Number: 6357
Abu Dharr reported Allah's Messenger (may peace be upon him) as saying: Abu Dharr, when you prepare the broth, add water to that and give that (as a present) to your neighbour.