Musnad Ahmad 4285

It was narrated that 'Abdullah said: The Messenger of Allah (ﷺ) said: Any two Muslims for whom three of their children die before reaching puberty, they will be a strong protection for them against the Fire.” Abu Dharr said: Two of my children died, O Messenger of Allah. He said: "And two.” Ubayy Abul-Mundhir, the leader of the prominent Qur'an reciters, said: One of my children died, O Messenger of Allah. He said: "And one, but that (i.e., the reward) is only (for showing patience) when calamity first strikes."