once
يَسْتَعِيذُ بِاللَّهِ و يَنْتَهِي عَمَّا شك فِيهِ
Meaning
(Say:) I seek refuge in Allah. (Then you should desist from doing what you are in doubt about.)
Source and references
Hisn al-Muslim, entry 133.The reference is copied from the edition; separate editorial verification is not complete yet.
Source edition: Fortress of the Muslim. Open source ↗