Riyad as-Saliheen 926
Usamah bin Zaid (May Allah be pleased with him) reported:
A grandson (child of the daughter) of the Messenger of Allah ﷺ was presented to him while the child was at his last breath. Tears began to flow from the eyes of the Messenger of Allah ﷺ. Sa'd said to him: "What is this, O Messenger of Allah?" He ﷺ said, "It is mercy which Allah has placed in the hearts of his salves. Allah bestows His Mercy on the merciful among His slaves."
[Al-Bukhari and Muslim].
وعن أسامة بن زيد رضي الله عنهما أن رسول الله ﷺ رفع إليه ابن ابنته وهو في الموت، ففاض عينا رسول الله ﷺ فقال له سعد: ما هذا يا رسول الله؟! قال:
"هذه رحمة جعلها الله تعالي في قلوب عباده الرحماء" ((متفق عليه)) .