Silsilat al-Ahadith al-Sahihah

It is narrated from Sayyiduna Ubayy bin Ka'b (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: "When Musa (peace be upon him) met Khidr (peace be upon him), a bird came and filled its beak with water from the sea. Khidr (peace be upon him) said to Musa (peace be upon him): Do you know what this bird wants to say? He said: What does it want to say? Khidr (peace be upon him) said: It is saying to me that your knowledge and mine, compared to the knowledge of Allah Almighty, is only as much as the water in my beak compared to the sea."