Sayyiduna Abu Sa'id (may Allah be pleased with him) said: Sayyiduna Husayn came while the Messenger of Allah (peace and blessings be upon him) was praying, and he clung to the neck of the Prophet (peace and blessings be upon him). He (peace and blessings be upon him) stood up with him on him and took hold of his hand, and kept holding him until he bowed (ruku').
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 2644