اللهُ اللهُ رَبِّي لَا أُشْرِكُ بِهِ شَيْئاً

Allāh, Allāh is my Lord, I do not associate anything with Him.

Reference: Allāh, Allāh is my Lord, I do not associate anything with Him. Abū Dāwud (#1525, 2/87). Also see _Ṣaḥīḥ Ibn Mājah_ (2/335).