Quran 18:66 · Al-Kahf

Moses was told about a further sign, i.e. that when he reached the required destination, the fish kept for eating would go down into the water in a peculiar manner. And at a certain place this was exactly what happened. But the fish was with the disciple and he could not for some reason inform Moses about this incident. After proceeding a little further, Moses came to know of this incident. He immediately returned to that place and found Khidr there, the person for whom he had undertaken such a long journey. God had bestowed on this servant, Khidr, special knowledge and powers, so that he could bring certain extraordinary influence to bear upon the affairs of this world. In view of this knowledge, he used to act against the customary norms. That is why, on Moses request to be allowed to accompany him, he said that he Moses would not be able to bear it.