I have not seen anyone more compassionate toward children than the Messenger of Allah ﷺ. Ibrahim had a wet nurse in the outskirts of Madinah, and he would go to visit him and we would go with him. He would enter the house, which would be filled with smoke, since the wet nurse's husband was a blacksmith. He would pick him up and kiss him, then return.
ما رأيت أحدا كان أرحم بالعيال من رسول الله ﷺ، قال: كان إبراهيم مسترضعا له في عوالي المدينة، فكان ينطلق ونحن معه، فيدخل البيت، وإنه ليدخن، وكان ظئره قينا، فيأخذه فيقبله، ثم يرجع.
Muslim narrated it in the Book of Virtues (2316) via Ismail (who is Ibn Ulaya), from Ayub, from Amr bin Saeed, from Anas, who related it.As for what is reported that Qasim bin Muhammad ﷺ completed his nursing in Paradise, this is a munkar (rejected) narration. Ibn Majah narrated it (1512) from Abdullah bin Imran, who said, Abu Dawud told us, Hisham bin Abu Walid told us, from his mother, from Fatimah bint Husayn, from her father Husayn bin Ali, who said, When Qasim, the son of the Messenger of Allah ﷺ, died, Khadijah said, "O Messenger of Allah, my milk has flowed for Qasim, so if only Allah had let him live until he completed his nursing." The Messenger of Allah ﷺ said, "His nursing will be completed in Paradise." She said, "If I knew that for certain, O Messenger of Allah, it would ease the matter for me." The Messenger of Allah ﷺ said, "If you wish, I will call upon Allah the Exalted and let you hear his voice." She said, "O Messenger of Allah, rather I believe Allah the Exalted and His Messenger."Hisham bin Abu Walid is Hisham bin Ziyad bin Abu Yazid, Abu Miqdam, of Madinah, and he is matruk (a discarded narrator).