Sahih Muslim Book 23, Hadith Number 5109.

Chapter : Excellence of sharing the small food.

Jabir b. ‘Abdullah reported: I heard Allah’s Messenger (may peace be upon him) as saying: Food for one person suffices two persons and food for two persons suffices four persons, and food for four persons suffices eight persons; and in the tradition transmitted on the authority of Ishaq there is no mention of the fact that he heard it directly (from the Holy Prophet).