اَللّٰهُمَّ اعْصِمْنِيْ مِنَ الشَّيْطَانِ الرَّجِيْمِ ـ

Allaahumma’-simnii minash-shaytaanir-rajiim. (Abu Hurayrah. Sunan Ibn Majah #765)

O Allah, protect me from the cursed Shaytan.

اَللّٰهُمَّ إِنِّيْ أَسْأَلُكَ مِنْ فَضْلِكَ ـ

Allaahumma innii as’aluka min fadlik. (Abu Humayd. Sahih Muslim #1165)

O Allah, I beg You for Your favor.

A person exiting the masjid should put his left foot out first and say this du’aa. Fadl refers to the bounties of this world.

(Source: Khalid Baig’s translation of du’aa #105, and translation and commentary of #106 from the Accepted Whispers: Munajat-e-Maqbul)