Sayyiduna Jubayr bin Mut'im (may Allah be pleased with him) narrates: I came to Madinah, when I came to it, and at that time I was not a Muslim. A severe drowsiness overcame me, and I slept in the mosque, until I was startled by the recitation of the Messenger of Allah (peace and blessings be upon him). He (peace and blessings be upon him) was reciting: "By the Mount, and by a Book inscribed." So I said: Inna lillahi wa inna ilayhi raji'un (We belong to Allah and to Him we return), until I left the mosque. And that was the first time Islam entered my heart.
Hadith Referenceالمعجم الكبير للطبراني / باب الجيم / 1572