He reported that the Messenger of Allah ﷺ was reciting Surah Sad while on the pulpit, and when he reached the verse of prostration, he came down and prostrated, and the people prostrated along with him.On another day, he recited it again, and when he reached the verse of prostration, the people prepared themselves to prostrate. The Prophet ﷺ said, "This is only the Tawba of a prophet, but I saw you preparing yourselves to prostrate." So he came down and prostrated, and they prostrated as well.
حدثنا أحمد بن صالح حدثنا ابن وهب أخبرني عمرو يعني ابن الحارث عن ابن أبي هلال عن عياض بن عبد الله بن سعد بن أبي سرح
أنه قال قرأ رسول الله ﷺ وهو على المنبر ص فلما بلغ السجدة نزل فسجد وسجد الناس معه فلما كان يوم آخر قرأها فلما بلغ السجدة تشزن الناس للسجود فقال النبي ﷺ إنما هي توبة نبي ولكني رأيتكم تشزنتم للسجود فنزل فسجد وسجدوا
Sourcing, hasan. Darimi narrated it, no. 1474, 1562, and Ibn Khuzayma, no. 1455, 1795, from the hadith of Saeed bin Abu Hilal by this route. Ibn Khuzayma criticized it and doubted its soundness, while Ibn Hibban graded it sahih, no. 689, 690, as did Hakim, 12/284, 285, saying it meets the standard of the two Shaykhs, and Dhahabi agreed with him. The hadith has supporting reports in Bayhaqi, 2/319, and elsewhere, and with these the hadith is hasan.