Imam Al-Nawawi’s Riyad-us-Saliheen
Supplication if one Fears (Harm)
981. Abu Musa Al-Ashari (May Allah be pleased with him) reported: When the Messenger of Allah (sallallaahu alayhi wa sallam), feared mischief from a people, he would supplicate: “Allahumma inna naj`aluka fi nuhurihim, wa na`udhu bika min shururihim (O Allah! We ask You to face them, and seek Your Protection against their evil.”
[Abu Dawud and An-Nasa’i].