Sa’eed ibn Jubayr said that he told Ibn Abbas (RA) that Nawf al-Bikali believed that Musa of the Banu Israel was not (the same as) Musa of Khidr, He replied, “The enemy of Allah lies.” Then he said that he had heard Ubayy ibn Ka’b say that he heard Allah’s Messenger (SAW) say: Musa stood up among the Banu Israel to deliver a sermon. He was asked, “Which of mankind is the most learned?” He said, “I am the most learned.” Allah admonished him for not attributing knowledge to Him (Allah). So Allah revealed to him, “A slave among My slaves at the meeting point of the two seas is more learned than you.” Musa said, “O Lord! How can I go to him?” He said to him, “Take a fish in your basket. Wherever you lose the fish - that is the place where he is” So he went with him went his servant he was Yusha’ ibn Nun Musa placed the fish in the basket and he and his servant departed. They walked till they came to a rock. Musa and his servant lied down there. The fish stirred within the basket and came out of it and dropped into the sea. Allah stopped the current of the water so that it was like a tunnel and there was a passage for the fish. For Musa and his servant it was strange. They departed walking the remainder of their day and their night, and the servant of Musa forgot to inform him. When it was morning, Musa said to his servant: "Bring us our breakfast, certainly we have encountered fatigue from this journey of ours.” (18:62) Indeed, Musa did not feel fatigued but only after they had gone past the place which they had been commanded to seek. The servant said: "Did you see when we took refuge on the rock, then I indeed forgot the fish - and none but Satan made me forget that I should speak of it - and it took its way into the sea; what a wonder!"(18:63) Musa said: "That is what we were seeking." (18: 64) “So they returned retracing their footsteps.” (18: 64) They both returned retracing their footsteps. Sufyan said that people imagine that at this rock lies the spring of life to which no dead thing is brought but it revives. The fish had been eaten partly but drops of; ter poured on it, it revived. So they retraced their footsteps till they were at the rock. They observed a man covered with a garment. Musa greeted him (with salaam). He asked, “is there (a greeting like) salaam on your land?’ He said, “I am Musa.” He asked, “Musa of Banu Israel?” He said, “Yes.” He said, “Musa, you have knowledge from Allah that Alalh taught you but He did not teach me. And, I possess knowledge from Allah that He taught me but did not teach you.” Musa pleaded: "May I follow you, so that you may teach me of what you have been taught of right judgment." (18:66) He said: "Surely you will not be able to bear with me patiently. And how can you have patience in that you have not encompassed in (your) knowledge?’ He said, “If Allah will you shall find me patient; and I shall not disobey you in any affair.” (18: 67-69) Khidr said in response to him: "If you follow me, question me not about anything until I muself mention it to you about it."(18: 70) He said, “Yes. So they - Khidr and Musa - departed walking along the coast, when a boat passed by them. They requested them to let them board it and they recognized Khidr and took them on board without any fare. Khidr pulled out a plank of the boat. Musa said to him, “These people took us in without fare but you damaged it with a hole that it may drown.” He added: "In order to drown its occupants. You have certainly done a grievous thing." (18: 71) He said: "Did I not say that you would not be able to bear with me patiently?" He (Musa) said: Reproach me not for what I forgot, and oppress me not in my affair distressingly." (18: 73) Then they came out of the boat. While they were walking along the coast, they came across a boy playing with other two lads. Khidr grabbed him by his head and jerked him by his hand and killed him. So, Musa said to him: "Have you slain an innocent person who has slain no one. Certainly you have done a horrible thing." (18: 74) He said reminding him: "Did I not say to you that you would not be able to bear with me patiently?" (18: 75) And, indeed, this was more severe than the first time. He (Musa) pleaded: If I question you about anything after this, keep not company with me; indeed you have received an excuse from me. ”So they departed until, when they came to the people of a township, they asked its people for food, but they refused to entertain them as guests. Then they found therein a wall about to fall down." (18: 76-77) That is, leaning down and Khidr gestured to it with his hand like this, "and so he set it up." (18:77) So, Musa protested, “A people to whom we came but they did not play host to us and did not serve us food.” And, also: if you had wished you could have taken a wage for it.” He (Khidr) said, “This is the parting between me and you. Now I will inform you the interpretation of that you were not able to bear patiently." (18: 77-78).
(Allah’s Messenger’s (SAW) narration continues :) May Allah have mercy on Musa! We wish that Musa had shown patience until (Allah) described to us more about the two of them! The first - it was from Musa’s forgetfulness. Then a swallow came and sitting on the edge of the boat, dipped its beak in the sea. Khidr thereupon said to Musa, “My knowledge and your knowledge have not lessened Allah’s knowledge even so much as this sparrow has withdrawn from the sea.” Sa’eed ibn Jubayr said that Ibn Abbas (RA) recited: "And there was before them a king who seized every perfect boat forcibly." And he recited: "And as for the lad, he was a disbeliever."
[Ahmed 21167, Bukhari 74, Muslim 2380, Abu Dawud 4707]