The Book of Prayer
Bulugh al-Maram #465
كتاب الصلاة
وَلِأَبِي دَاوُدَ, وَاَلتِّرْمِذِيِّ نَحْوُهُ عَنْ عَائِشَةَ وَفِيهِ: «كُلَّ سُورَةٍ فِي رَكْعَةٍ, وَفِي اَلْأَخِيرَةِ:»قُلْ هُوَ اَللَّهُ أَحَدٌ«, وَالْمُعَوِّذَتَيْنِ»
Abu Dawud and at-Tirmidhi report something similar from 'Aishah (RA) that Allah's Messenger (ﷺ) used to recite a Surat in every Rak'at and in the last (third) Rak'at he would recite Qul Huwa Allahu Ahad (Surat al-Ikhlas) and al-Mu'awwidhatain.
وَلِأَبِي دَاوُدَ, وَاَلتِّرْمِذِيِّ نَحْوُهُ عَنْ عَائِشَةَ وَفِيهِ: "كُلَّ سُورَةٍ فِي رَكْعَةٍ, وَفِي اَلْأَخِيرَةِ: "قُلْ هُوَ اَللَّهُ أَحَدٌ", وَالْمُعَوِّذَتَيْنِ"
Abu Dawud and at-Tirmidhi report something similar from 'Aishah (RA) that Allah's Messenger (ﷺ) used to recite a Surat in every Rak'at and in the last (third) Rak'at he would recite Qul Huwa Allahu Ahad (Surat al-Ikhlas) and al-Mu'awwidhatain.
— Bulugh al-Maram, Hadith 465