Sunan Ibn Majah, Chapter: Chapters Regarding Funerals

"The son of one of the daughters of the Messenger of Allah (saw) was dying. She sent for him, asking him to come to her, and he sent word to her, saying: 'To Allah belongs what He has taken and to Him belongs what He has given. Everything has an appointed time with Him, so be patient and seek reward.' But she sent for him again, adjuring him to come. So the Messenger of Allah (saw) got up, and I got up with him, as did Mu'adh bin Jabal, Ubayy bin Kab and Ubadah bin Samit. When we entered they handed the child to the Messenger of Allah (saw), and his soul was rattling in his chest." I think he was that it was like a water skin. "The Messenger of Allah (saw) wept, and Ubadah bin Samit said to him: 'What is this, O Messenger of Allah?' He said: 'It is compassion which Allah has created in the son of Adam. Allah only shows mercy to those of His slaves who are compassionate.'" Daif