Al-Baqarah 2:239

Fa-in khiftum farijalan aw rukbananfa-itha amintum fathkuroo Allaha kamaAAallamakum ma lam takoonoo taAAlamoon

And if you fear [an enemy, then pray] on foot or riding. But when you are secure, then remember Allāh [in prayer], as He has taught you that which you did not [previously] know.

But if you are in fear, then (pray) on foot or riding. But when you are in peace, recite Allah’s name as He has taught you what you did not know.