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: 6365
Abu Huraira reported Allah's Apostle (may peace be upon him) as saying: Anyone amongst the Muslims, three of whose children die, and he resigns himself calmly to the will of God, Fire will not touch him but for the fulfilment of the oath.