لا إِلـهَ إِلاّ اللهُ الـواحِدُ القَهّـار رَبُّ السَّـمواتِ وَالأرْضِ وَما بَيْـنَهـما العَزيـزُ الغَـفّار
Lā ilāha illallāh al-Wāḥidul-Qahhār, Rabbus-samāwāti wa ‘l-arḍi wa mā baynahuma al-`Azīzul-Ghaffār.
There is none worthy of worship but Allah, the One, the Victorious, Lord of the heavens and the earth and all that is between them, the All-Mighty, the All-Forgiving.
This is to be said if you turn over in bed during the night. Al-Hakim graded it authentic and Ath-Thahabi agreed 1/540. Also see An-Nasa'i, 'Amalul-Yawm wal-Laylah, and Ibn As-Sunni. See also Al-Albani, Sahihul-Jami' As-Saghir 4/ 213.