ENOfficial
It was narrated that 'Aishah said: "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."
Source: sunnah.com
Other translations
Arabic
أَخْبَرَنَا قُتَيْبَةُ، عَنْ مَالِكٍ، عَنْ صَالِحِ بْنِ كَيْسَانَ، عَنْ عُرْوَةَ، عَنْ عَائِشَةَ، قَالَتْ فُرِضَتِ الصَّلاَةُ رَكْعَتَيْنِ رَكْعَتَيْنِ فَأُقِرَّتْ صَلاَةُ السَّفَرِ وَزِيدَ فِي صَلاَةِ الْحَضَرِ .
sunnah.com