Umm Salamah (RA) narrated that: When the Prophet (ﷺ) would leave his house, he would say:
بِسْمِ اللَّهِ تَوَكَّلْتُ عَلَى اللَّهِ اَللَّـهُمَّ إِنَّا نَعُوذُ بِكَ مِنْ أَنْ نَزِلَّ أَوْ نَضِلَّ أَوْ نَظْلِمَ أَوْ نُظْلَمَ أَوْ نَجْهَلَ أَوْ يُجْهَلَ عَلَيْنَا
بِسْمِ اللّٰهِ تَوَكَّلْتُ عَلَى اللّٰهِ اَللّٰهُمَّ اِنَّا نَعُوْذُ بِكَ مِنْ اَنْ نَزِلَّ اَوْ نَضِلَّ اَوْ نَظْلِمَ اَوْ نُظْلَمَ اَوْ نَجْهَلَ اَوْ يُجْهَلَ عَلَيْنَا
Bismillaahi, tawakkaltu 'alal-laahi. Allaahumma, inna na`udhu bika min an nazilla aw nadilla, aw nazlima aw nuzlama, aw najhala aw yujhala 'alaina
In the Name of Allah, I place my trust in Allah. O Allah! We seek refuge in You from slipping unintentionally or becoming misguided, or committing oppression or being oppressed, or acting ignorantly or being treated ignorantly.
A mu'min should recite these adhkar by his/her heart whenever (Day/Night) he/she goes outside.