The Holy Quran 4:101 — Surah An-Nisa

Arabic text

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

Translation

When you travel (more than 88km) on earth (for whatever purposes), there is no sin on you should you shorten (reduce) your salaah if you fear an attack from the Kuffaar. Indeed the Kuffaar are your open enemies.

Tafsir (excerpt) — Tafsir Usmani

The ruling on qasr (shortening) of the prayer: that is, when you travel for jihad (striving in the path of Allah) and the like, and fear that the disbelievers, who are your open enemies, will seize an opportunity to harass you, then shorten the prayer, that is, a prayer which at home is of four rak'ahs (units of prayer), pray it as two rak'ahs.

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