Musannaf Ibn Abi Shaybah

Hazrat Abdullah bin Masood (may Allah be pleased with him) narrates that when Hazrat Musa was sent to Pharaoh, he said: "My Lord! What should I recite?" Allah said: "Say: Haya Sharran Haya." A'mas says its meaning is: "O the Being! Who was alive before everything and will remain alive after everything perishes."