(Say:) I seek refuge in Allah. (Then you should desist from doing what you are in doubt about.)
Reference:Al-Bukhari, cf. Al-Asqalani, Fathul-Bari 6/336, Muslim 1/120.Hisnul Muslim 133
أَعـوذُ بِاللهِ
A`ūdhu billāh
(Say:) I seek refuge in Allah. (Then you should desist from doing what you are in doubt about.)