Sayyiduna Afif (may Allah be pleased with him), who was the maternal half-brother of al-Ash'ath bin Qays, said: I came to Makkah to buy perfume and scent for my family, and I stayed with Abbas bin Abd al-Muttalib, who was a merchant. I was with him, and the sun had risen. As I was watching, a young man came. He turned his gaze towards the sky, then directed his gaze towards the Ka'bah. Only a short while passed before a boy came and stood on his right. Only a short while passed before a woman came and stood behind the two of them. The young man said the takbir, and the two of them said the takbir; then he bowed and the two of them bowed; then he prostrated and the two of them prostrated. I said: "O Abbas, this is a great matter." Abbas said: "A great matter. Do you know this young man?" I said: "No." He said: "This is Muhammad bin Abdullah bin Abd al-Muttalib, my brother's son. Do you know who this woman is?" I said: "No." He said: "This is Khadijah bint Khuwaylid bin Asad bin Abd al-Uzza, the leader of the women of Quraysh, the wife of my nephew. And this is Ali bin Abi Talib, my brother's son. My nephew claims that his Lord, the Lord of the heavens and the earth, has commanded him with this religion. No, by Allah, I do not know anyone on the face of the earth following this religion except these three."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 15273