Musnad Ahmad 1153:1207

Qurrad Abu Nuh narrated to us, 'Ikrimah ibn 'Ammar informed us, from Yahya ibn Abi Kathir, from Abu Salamah ibn 'Abd al-Rahman ibn 'Awf, who said: I asked 'A'ishah, the Mother of the Believers: With what did the Messenger of Allah, may Allah bless him and grant him peace, begin his prayer when he stood at night? She said: When he stood, he would say the takbir, and say: "O Allah, Lord of Jibril, Mika'il, and Israfil, Creator of the heavens and the earth, Knower of the unseen and the witnessed, You judge between Your servants concerning that wherein they used to differ. Guide me to that which has been differed upon of the truth by Your permission, for indeed You guide whom You will to a straight path."