ENOfficial
Ubayy b. Ka'b said, “Prayer in a single garment was a practice we followed along with God’s Messenger, and no blame was cast on us.” Ibn Mas'ud said, “That was only when clothing was scarce, but when God enlarged our circumstances prayer in two garments became purer.” Ahmad transmitted it.
Source: sunnah.com
Other translations
Arabic
وَعَنْ أُبَيِّ بْنِ كَعْبٍ قَالَ: الصَّلَاةُ فِي الثَّوْبِ الْوَاحِدِ سُنَّةٌ كُنَّا نَفْعَلُهُ مَعَ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ وَلَا يُعَابُ عَلَيْنَا. فَقَالَ ابْنُ مَسْعُودٍ: إِنَّمَا كَانَ ذَاكَ إِذْ كَانَ فِي الثِّيَاب قلَّة فَأَما إِذْ وَسَّعَ اللَّهُ فَالصَّلَاةُ فِي الثَّوْبَيْنِ أَزْكَى. رَوَاهُ أَحْمد
sunnah.com