Surah Al-Haqqah · 69:43

“I crept up on the Messenger of Allah ﷺ, and he was reciting Surah al-Haqqah; I marveled at the eloquence of the Qur'an, saying to myself, "By Allah, this is a poet, as the Quraysh claim." He recited: "And it is not the word of a poet; little do you believe." I said, "He is a soothsayer." He recited: "Nor the word of a soothsayer; little do you remember." ... So Islam entered my heart.”

Same source as the post on this event that carries this ayah.

Same source as the post on this event that carries this ayah.