Al Baqarah, 239 Ayah
2:239
فَإِنۡ خِفۡتُمۡ فَرِجَالًا أَوۡ رُكۡبَانٗاۖ فَإِذَآ أَمِنتُمۡ فَٱذۡكُرُواْ ٱللَّهَ كَمَا عَلَّمَكُم مَّا لَمۡ تَكُونُواْ تَعۡلَمُونَ ٢٣٩
Fa'in Khiftum Farijālāan 'Aw Rukbānāan ۖ Fa'idhā 'Amintum Fādhkurū Al-Laha Kamā `Allamakum Mā Lam Takūnū Ta`lamūna
And if you fear [an enemy, then pray] on foot or riding. But when you are secure, then remember Allah [in prayer], as He has taught you that which you did not [previously] know.