Abu Hurayrah recited Sūrat al-Inshiqāq and then prostrated. After he finished the prostration, he told them that the Messenger of Allah (may Allah’s peace and blessings be upon him) had prostrated when he recited it

Abu Hurayrah (may Allah be pleased with him) mentioned that he recited Sūrat al-Inshiqāq and then prostrated when he reached the verse that says: {And when the Qur’an is recited to them, they do not prostrate [to Allah ]?} [Sūrat al-Inshiqāq: 21]
Abu Rāfi‘ then questioned him regarding this prostration after recitation of that verse. In another narration, Abu Rāfi‘ asked why he prostrated. He asked him because it was narrated that the Prophet (may Allah's peace and blessings be upon him) had not prostrated while reciting the small Sūrahs since he emigrated to Madīnah.
Abu Hurayrah then said: "If I had not seen the Messenger (may Allah's peace and blessings be upon him) prostrate, I would not have prostrated." In other words, he only prostrated because he had seen the Messenger (may Allah's peace and blessings be upon him) prostrate.