Moses said to him, "May I follow you on [the condition] that you teach me from what you have been taught of sound judgement?"

     [Moses] said, "That is what we were seeking." So they returned, following their footprints. And they found a servant from among Our servants [i.e., al-Khidhr] to whom We had given mercy from Us and had taught him from Us a [certain] knowledge. Moses said to him, "May I follow you on [the condition] that you teach me from what you have been taught of sound judgement?" 

THE QUR'AN al-Kahf 18:64-66