Abdullah bin Abbas reported,

He and Hurr bin Qays bin Hisn al-Fazari had a dispute about the companion of Musa . Ibn Abbas said, "He was al-Khidr."Then Ubayy bin Kaab al-Ansari passed by them, and Ibn Abbas called out to him, saying, "Abu Tufayl, come over to us. My companion and I have been disputing about the companion of Musa, the one whom Musa asked for a way to meet. Did you hear the Messenger of Allah ﷺ mention his story?"Ubayy replied, "I heard the Messenger of Allah ﷺ say, 'While Musa was among a gathering of the Children of Israil, a man came to him and asked, "Do you know anyone more knowledgeable than yourself?" Musa answered, "No." So Allah revealed to Musa, "Yes, Our servant al-Khidr." Musa then asked for a way to meet him, and Allah made the fish a sign for him. He was told, "When you lose the fish, turn back, for you will meet him there." Musa traveled as long as Allah willed him to travel, then he said to his servant, "Bring us our morning meal" [Kahf 18:62]. When Musa asked for the meal, his servant said, "Did you see when we took refuge at the rock? Indeed, I forgot the fish, and none made me forget to mention it but Satan" [Kahf 18:63]. Musa said to his servant, "That is what we were seeking. So they returned, retracing their footsteps" [Kahf 18:64]. They found al-Khidr, and what happened between them was as Allah recounted in His Book.'"Except that Yunus said, "He was following the trail of the fish in the sea."

حدثني حرملة بن يحيى أخبرنا ابن وهب أخبرني يونس عن ابن شهاب عن عبيد الله بن عبد الله بن عتبة بن مسعود

عن عبد الله بن عباس

أنه تمارى هو والحر بن قيس بن حصن الفزاري في صاحب موسى عليه السلام فقال ابن عباس هو الخضر فمر بهما أبي بن كعب الأنصاري فدعاه ابن عباس فقال يا أبا الطفيل هلم إلينا فإني قد تماريت أنا وصاحبي هذا في صاحب موسى الذي سأل السبيل إلى لقيه فهل سمعت رسول الله ﷺ يذكر شأنه فقال أبي سمعت رسول الله ﷺ يقول بينما موسى في ملإ من بني إسرائيل إذ جاءه رجل فقال له هل تعلم أحدا أعلم منك قال موسى لا فأوحى الله إلى موسى بل عبدنا الخضر قال فسأل موسى السبيل إلى لقيه فجعل الله له الحوت آية وقيل له إذا افتقدت الحوت فارجع فإنك ستلقاه فسار موسى ما شاء الله أن يسير ثم قال لفتاه {آتنا غداءنا} فقال فتى موسى حين سأله الغداء {أرأيت إذ أوينا إلى الصخرة فإني نسيت الحوت وما أنسانيه إلا الشيطان أن أذكره} فقال موسى لفتاه {ذلك ما كنا نبغي فارتدا على آثارهما قصصا} فوجدا خضرا فكان من شأنهما ما قص الله في كتابه إلا أن يونس قال فكان يتبع أثر الحوت في البحر