Musannaf Ibn Abi Shayba 21:503

Muhammad ibn Bishr narrated to us, Mis'ar narrated to us, from Alqama ibn Marthad, from Ibn Sabit, who said: Khalid ibn al-Walid suffered from insomnia, so the Prophet, peace and blessings of Allah be upon him, said to him: "Shall I not teach you words that, if you say them, you will sleep? 'O Allah, Lord of the heavens and what they shade, and Lord of the earths and what they carry, and Lord of the devils and what they lead astray, be a protector for me from the evil of all of Your creation, lest any one of them should hasten against me or transgress. Mighty is Your protection, and there is no god other than You.'"