"Allah, the Mighty and Sublime, enjoined the prayer on the tongue of your Prophet ﷺ: While a resident four (rak'ahs), while traveling two, and at times of fear one." (Using translation from Nasāʾī 1442)
إِنَّ اللهَ ﷻ فَرَضَ الصَّلاةَ عَلَى لِسَانِ نَبِيِّكُمْ ﷺ فِي الْحَضَرِ أَرْبَعًا وَفِي السَّفَرِ رَكْعَتَيْنِ وَفِي الْخَوْفِ رَكْعَةً