Ya’la al-Aamiri narrates that they (with a group of companions) had gone out with the Prophet to a meal, and Hussain was playing in the street. The Prophet came in front of the people and stretched out his hands, and the child (Hussain) started to run here and there. The Prophet made him laugh until he caught him, then he put one hand under his chin and the other on his head and kissed him, and said, “Hussain is from me and I am from Hussain. Allah loves anyone who loves Hussain. Hussain is a grandson among the grandsons.”

Sunan ibn Majah, vol. 1, p. 51, H. 144
Al-Mustadrak ala al-Sahihayn, vol. 3, p. 94, H. 4820