Musnad Ahmed: Hadith 3531

The Messenger of Allah (ﷺ) said: "There is no one among the Muslims, three of whose children die before reaching puberty, but they will be a strong protection against the Fire for him." It was said: O Messenger of Allah, what if they were two? He said: "Even if they were two." Abu Dharr (رضي الله عنه) said: O Messenger of Allah, I have only sent two ahead of me. He said: "Even if they were two.” Ubayy bin Kab Abu-Mundhir, the leader of the prominent scholars, said: I only sent one ahead of me. It was said to him. Even if it was one? He said: "That (i.e., the reward) is only (for showing patience) when calamity first strikes."