Bismillāhi, tawakkaltu `alallāhi,
wa lā ḥawla wa lā quwwata illā billāh.
In the Name of Allah, I have placed my trust in Allah,
there is no might and no power except by Allah.
Reference:
Abu Dawud 4/325, At-Tirmidhi 5/490. See also Al-Albani, Sahih At-Tirmidhi
3/151