Sahih Muslim Book 32, Hadith Number 6365.

Chapter : The merit of one who resigns himself to the will of God calmly at the time of the death of one’s son.

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.