An-Nisa' - 4:101

وَإِذَا ضَرَبْتُمْ فِي الأَرْضِ فَلَيْسَ عَلَيْكُمْ جُنَاحٌ أَن تَقْصُرُواْ مِنَ الصَّلاَةِ إِنْ خِفْتُمْ أَن يَفْتِنَكُمُ الَّذِينَ كَفَرُواْ إِنَّ الْكَافِرِينَ كَانُواْ لَكُمْ عَدُوًّا مُّبِينًا
[4:101]
And when you journey in the earth, there is no blame on you if you shorten the prayer, if you fear that those who disbelieve will cause you distress, surely the unbelievers are your open enemy.
When ye travel through the earth, there is no blame on you if ye shorten your prayers, for fear the Unbelievers May attack you: For the Unbelievers are unto you open enemies.
And when ye go forth in the land, it is no sin for you to curtail (your) worship if ye fear that those who disbelieve may attack you. In truth the disbelievers are an open enemy to you.