فَإنْ خِفْتُمْ فَرِجَالاً أَوْ رُكْبَانًا فَإِذَا أَمِنتُمْ فَاذْكُرُواْ اللّهَ كَمَا عَلَّمَكُم مَّا لَمْ تَكُونُواْ تَعْلَمُونَ
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سورة البقرة
(2/239) And if you fear (vital danger) then (perform your prayers) while on foot or riding. And when you are in safety, then remember Allah in the manner He has taught you what you did not know (how you will remember Allah).
Surah Al-Baqarah