((Imām Bukhārī narrates) that) Muhammad ibn Ghurair al-Zuhrī narrated to us, he said: Ya'qūb ibn Ibrāhīm narrated to us, he said: My father narrated to me, from Sālih, from Ibn Shihāb, he narrated that 'Ubaidullāh ibn 'Abdullāh informed him, from Ibn 'Abbās, may Allāh be pleased with them both:

that a discussion took place between him and Hurr ibn Qais ibn Hisn al-Fazārī regarding the companion of Mūsā. Ibn 'Abbās said: The companion of Mūsā was Khidr. Ubayy ibn Ka'b, may Allāh be pleased with him, passed by them. Ibn 'Abbās called him and said: A discussion has taken place between me and this companion of mine regarding Mūsā, upon him peace, whom he asked about the path to meet him. Have you heard the Prophet ﷺ say something about him? Ubayy said: Yes! I heard the Messenger of Allāh ﷺ saying that at the time when Mūsā was in a gathering of Banī Isrā'īl, a person came and asked him: Do you know of anyone more knowledgeable than you? Mūsā said: No. So Allāh the Exalted revealed to Mūsā: Yes indeed! Our servant Khidr (is more knowledgeable than you). So Mūsā asked about the way to him, and Allāh the Exalted made the fish a sign for him, and it was said to him: Wherever you find this fish lost, return from there, then soon you will meet him. He was going along the sea following the trail of the fish, then his student (Yūsha' ibn Nūn) said to Mūsā: "Did you see, when we were resting leaning against the rock, there I forgot to mention the fish, and indeed it was only Satan who made me forget to mention it. Mūsā said: That is what we were seeking. So they returned, retracing their footsteps." (Al-Kahf: -). Then the two of them found Khidr. Then there is that account of their conversation which Allāh, Mighty and Glorious, has related in His Book.