"The Salah was enjoined two Rak'ahs at a time, then the Salah when traveling remained like that, but the Salah while resident was increased." (Using translation from Nasāʾī 455)  

«فُرِضَتِ الصَّلَاةُ رَكْعَتَيْنِ فَأُقِرَّتْ صَلَاةُ السَّفَرِ وَزِيدَ فِي صَلَاةِ الْحَضَرِ»  

"The Salah was enjoined on the lips of the Prophet ﷺ, four Rak'ahs while resident, and two while traveling, and one Rak'ah during times of fear." (Using translation from Nasāʾī 456)  

«وَفُرِضَتِ الصَّلَاةُ عَلَى لِسَانِ النَّبِيِّ ﷺ فِي الْحَضَرِ أَرْبَعًا وَفِي السَّفَرِ رَكْعَتَيْنِ وَفِي الْخَوْفِ رَكْعَةٌ»