An-Nisa 4:101

وَإِذَا ضَرَبۡتُمۡ فِي ٱلۡأَرۡضِ فَلَيۡسَ عَلَيۡكُمۡ جُنَاحٌ أَن تَقۡصُرُواْ مِنَ ٱلصَّلَوٰةِ إِنۡ خِفۡتُمۡ أَن يَفۡتِنَكُمُ ٱلَّذِينَ كَفَرُوٓاْۚ إِنَّ ٱلۡكَٰفِرِينَ كَانُواْ لَكُمۡ عَدُوّٗا مُّبِينٗا 101

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