Usama b. Zaid said:
I went to the Prophet one night about something I required and he came out with something (I did not know what) under his cloak. When I had finished telling him my business, I asked him what he had under his cloak, and when he opened it, I saw al-Hasan and al-Husain on his hips. He then said, "These are my sons and my daughter's sons. 0 God, I love them, so I beseech Thee to love them and those who love them."
Tirmidhi transmitted it.