To visit sick children

Narrated Abu 'Uthman:

Usama bin Zaid said that while he. Sad and Ubai bin Ka'b were with the Prophet a daughter of the Prophet sent a message to him, saying. 'My daughter is dying;
please come to us." The Prophet sent her his greetings and added "It is for Allah what He takes, and what He gives;
and everything before His sight has a limited period. So she should hope for Allah's reward and remain patient." She again sent a message, beseeching him by Allah, to come. So the Prophet got up. and so did we (and went there). The child was placed on his lap while his breath was irregular. Tears flowed from the eyes of the Prophet. Sad said to him, "What is this, O Allah's Apostle?" He said. "This Is Mercy which Allah has embedded in the hearts of whomever He wished of His slaves. And Allah does not bestow His Mercy, except on the merciful among His slaves. (See Hadith No. 373 Vol. 2)

حَدَّثَنَا حَجَّاجُ بْنُ مِنْهَالٍ، حَدَّثَنَا شُعْبَةُ، قَالَ أَخْبَرَنِي عَاصِمٌ، قَالَ سَمِعْتُ أَبَا عُثْمَانَ، عَنْ أُسَامَةَ بْنِ زَيْدٍ ـ رضى الله عنهما ـ أَنَّ ابْنَةً لِلنَّبِيِّ، ﷺ أَرْسَلَتْ إِلَيْهِ وَهْوَ مَعَ النَّبِيِّ ﷺ وَسَعْدٍ وَأُبَىٍّ نَحْسِبُ أَنَّ ابْنَتِي قَدْ حُضِرَتْ فَاشْهَدْنَا فَأَرْسَلَ إِلَيْهَا السَّلاَمَ وَيَقُولُ " إِنَّ لِلَّهِ مَا أَخَذَ وَمَا أَعْطَى وَكُلُّ شَىْءٍ عِنْدَهُ مُسَمًّى فَلْتَحْتَسِبْ وَلْتَصْبِرْ ". فَأَرْسَلَتْ تُقْسِمُ عَلَيْهِ، فَقَامَ النَّبِيُّ ﷺ وَقُمْنَا، فَرُفِعَ الصَّبِيُّ فِي حَجْرِ النَّبِيِّ ﷺ وَنَفْسُهُ تَقَعْقَعُ فَفَاضَتْ عَيْنَا النَّبِيِّ ﷺ فَقَالَ لَهُ سَعْدٌ مَا هَذَا يَا رَسُولَ اللَّهِ قَالَ " هَذِهِ رَحْمَةٌ وَضَعَهَا اللَّهُ فِي قُلُوبِ مَنْ شَاءَ مِنْ عِبَادِهِ، وَلاَ يَرْحَمُ اللَّهُ مِنْ عِبَادِهِ إِلاَّ الرُّحَمَاءَ ".