Sahih Muslim Book 32, Hadith Number 6368.
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 Sa’id Khudri reported that a woman came to Allah’s Messenger (may peace be upon him) and said: Allah’s Messenger, men receive your instructions; kindly allocate at your convenience a day for us also, on which we would come to you and you would teach us what Allah has taught you. He said: You assemble on such and such a day. They assembled and Allah’s Messenger (may peace be upon him) came to them and taught them what Allah had taught him and he then said: No woman amongst you who sends her three children as her forerunners (in the Hereafter) but they would serve him as a protection against Hell-Fire. A woman said: What about two and two and two? Thereupon Allah’s Messenger (may peace be upon him) said: Even if they are two and two and two.