Fiqh-us-Sunnah Volume 4, Funerals and Dhikr, Fiqh 4.025B.
Section : The Reward of a Person Losing a Child.
Bukhari reported from Anas that the Prophet, peace be upon him, said: “A Muslim who loses three of his children before they come of age will be brought to Paradise by Allah as a mercy to him for losing them.”
Bukhari and Muslim reported from Abu Sa’id al-Khudri that he said: “Some women asked the Prophet, peace be upon him: ‘Appoint a (separate) day to (admonish) us.’ The Prophet, peace be upon him, told them: ‘If a (Muslim) woman’s three children die, they will be a protection for her from Hell.’ A woman asked him, ‘And what if two of her children die?’ He replied: ‘And (even) if two of her children die’.”