That the Prophet (ﷺ) used to take him and Al-Hasan, and used to say, "O Allah! I love them, so please love them," or said something similar.
Sahih al-Bukhari Book 62, Hadith 92
← Previous Hadith I heard the Prophet (ﷺ) talking at the pulpit while Al-Hasan was sitting beside him, and he (i.e. the Prophet ) was once looking at the people and at another time Al-Hasan, and saying, "This son of mine is a Saiyid (i.e. chief) and perhaps Allah will bring about an agreement between two sects of the Muslims through him."

Sahih al-Bukhari Book 62, Hadith 91 Next Hadith → Anas bin Malik said, "The head of Al-Husain was brought to 'Ubaidullah bin Ziyad and was put in a tray, and then Ibn Ziyad started playing with a stick at the nose and mouth of Al-Husain's head and saying something about his handsome features." Anas then said (to him), "Al-Husain resembled the Prophet more than the others did." Anas added, "His (i.e. Al-Husain's) hair was dyed with Wasma (i.e. a kind of plant used as a dye).

Sahih al-Bukhari Book 62, Hadith 93