بُلُوغُ الْمَرَامِ
Bulugh al-Maram 394
The Book of Prayer
وَلَهُ عَنْهَا: { مَا رَأَيْتُ رَسُولَ اَللَّهِ - صلى الله عليه وسلم -يُصَلِّي سُبْحَةَ اَلضُّحَى قَطُّ, وَإِنِّي لَأُسَبِّحُهَا } [1] .
In yet another narration of Muslim from her: ['Aishah (RA)] said, "I have never seen Allah's Messenger (ﷺ) offering Duha prayer, yet I offer it."
Sunnah.com reference: Book 2, Hadith 298