I saw the Messenger of Allah ﷺ on the pulpit addressing the people when Hasan bin Ali, may Allah be pleased with him, came out with a piece of cloth around his neck trailing behind him. He tripped over it and fell on his face. The Messenger of Allah ﷺ came down from the pulpit heading toward him. When the people saw this, they picked the boy up and brought him to him. He carried him and said, "May Allah destroy Satan. Indeed, a child is a trial. By Allah, I was not aware that I had come down from the pulpit until he was brought to me."
رأيت رسول الله ﷺ على المنبر يخطب الناس، فخرج الحسن بن علي رضي الله تعالى عنه في عنقه خرقة يجرها، فعثر فيها فسقط على وجهه، فنزل رسول الله ﷺ عن المنبر يريده، فلما رآه الناس أخذوا الصبي فأتوه به، فحمله، فقال: قاتل الله الشيطان، إن الولد فتنة، والله ما علمت أني نزلت عن المنبر حتى أوتيت به.
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Tabarani related it in al-Kabir (33/3–34), from Abdullah bin Ali Jarudi Nisaburi, who said, Ahmad bin Hafs narrated to us, my father narrated to me, Ibrahim bin Tahman narrated to us, from Abbad bin Ishaq, from Zayd bin Abu Attab, from Ubayd bin Jurayj, from Abdullah bin Umar, who mentioned it.Its isnad is hasan because of Ahmad bin Hafs (he is the son of Abdullah bin Rashid Sulami), his father, and Abbad bin Ishaq (whose name is Abdul-Rahman, Abbad being a nickname for him), for all of these are hasan in their hadith.It was narrated from Ibn Abbas, who said, "The Messenger of Allah ﷺ was carrying Hasan bin Ali on his shoulder, and a man said, 'What a fine mount you are riding, boy!' The Prophet ﷺ said, 'And what a fine rider he is.'"Tirmidhi related it (3784), from Muhammad bin Bashshar, who said, Abu Amir Aqadi narrated to us, who said, Zama bin Salih narrated to us, from Salama bin Wahram, from Ikrima, from Ibn Abbas, who mentioned it.He said, "This is a rare hadith, we know it only through this route, and Zama bin Salih has been graded daif by some scholars of hadith on account of his memory."And it is as he said, for Zama bin Salih is daif by consensus of the scholars.As for Hakim, he graded it sahih through this route (3/170), but Dhahabi challenged him by saying, "No." meaning it is not sahih.