Hadith 988
Sayyiduna Ubayy bin Ka'b (may Allah be pleased with him) narrates: Whenever the Prophet Muhammad (peace be upon him) mentioned any of the previous prophets, he would first mention himself. One day he said: "May Allah have mercy on us and on Sayyiduna Musa (peace be upon him). If he had been patient with his companion (i.e., Sayyiduna Khidr, peace be upon him), he would have seen amazing things himself. But he said: 'If I ask you about anything after this, then do not keep me with you.'"