An-Nisa 4:101

وَإِذَا ضَرَبْتُمْ فِى ٱلْأَرْضِ فَلَيْسَ عَلَيْكُمْ جُنَاحٌ أَن تَقْصُرُوا۟ مِنَ ٱلصَّلَوٰةِ إِنْ خِفْتُمْ أَن يَفْتِنَكُمُ ٱلَّذِينَ كَفَرُوٓا۟ ۚ إِنَّ ٱلْكَـٰفِرِينَ كَانُوا۟ لَكُمْ عَدُوًّا مُّبِينًا

Wa-idhā ḍarabtum fī l-arḍi falaysa ʿalaykum junāḥun an taqṣurū mina l-ṣalati in khif'tum an yaftinakumu alladhīna kafarū inna l-kāfirīna kānū lakum ʿaduwwan mubīnan

And when you travel throughout the land, there is no blame upon you for shortening the prayer, [especially] if you fear that those who disbelieve may disrupt [or attack] you. Indeed, the disbelievers are ever to you a clear enemy.