Musannaf Ibn Abi Shayba 21:200

Ibn Fudayl narrated to us, from Layth, from Khalid bin Sa'id bin al-Musayyib, who said: Sa'id said: I entered the mosque while I thought that it was morning, but it was still a long night, and there was no one in it except me. So I stood up, and I heard a movement behind me, and I became frightened. He said: "O you whose heart is filled with fear, do not fear and do not be alarmed. Say: 'O Allah, You are the Sovereign, the All-Powerful; whatever You will of a matter, it comes to be.' Then ask for whatever appears to you [to ask for]." Sa'id said: So I did not ask Allah for anything except that He answered me.