سورة النساء

وَإِذَا ضَرَبْتُمْ فِي الْأَرْضِ فَلَيْسَ عَلَيْكُمْ جُنَاحٌ أَنْ تَقْصُرُوا مِنَ الصَّلَاةِ إِنْ خِفْتُمْ أَنْ يَفْتِنَكُمُ الَّذِينَ كَفَرُوا ۚ إِنَّ الْكَافِرِينَ كَانُوا لَكُمْ عَدُوًّا مُبِينًا ﴿١٠١﴾

Surah an-Nisa'

101. When you travel in the land, there is no blame on you for shortening the prayer, if you fear that the unbelievers may attack you. The unbelievers are your obvious enemies.