Surah An-Nisa Verse 101 - English Translation by Aisha Bewley
Surah An-Nisaوَإِذَا ضَرَبۡتُمۡ فِي ٱلۡأَرۡضِ فَلَيۡسَ عَلَيۡكُمۡ جُنَاحٌ أَن تَقۡصُرُواْ مِنَ ٱلصَّلَوٰةِ إِنۡ خِفۡتُمۡ أَن يَفۡتِنَكُمُ ٱلَّذِينَ كَفَرُوٓاْۚ إِنَّ ٱلۡكَٰفِرِينَ كَانُواْ لَكُمۡ عَدُوّٗا مُّبِينٗا
When you are travelling in the land, there is nothing wrong in your shortening your salat if you fear that those who are kafir may harass you. The kuffar are your clear-cut enemies