Ayesha reported,

I never saw the Messenger of Allah ﷺ perform the forenoon prayer, though I myself perform it. The Messenger of Allah ﷺ would sometimes leave a deed he loved to do, fearing that people would adopt it and it would then be made obligatory upon them.

Muslim 1662

Sahih

حدثنا يحيى بن يحيى قال قرأت على مالك عن ابن شهاب عن عروة

عن عائشة أنها قالت

ما رأيت رسول الله ﷺ يصلي سبحة الضحى قط وإني لأسبحها وإن كان رسول الله ﷺ ليدع العمل وهو يحب أن يعمل به خشية أن يعمل به الناس فيفرض عليهم

مسلم 1662صحيح
Contents
Reference
Commentary
Ayat
Collection
Sahih Muslim
Book
Travelers' prayer and its shortening
Chapter
Recommendation of Duha prayer, that its minimum is two rakahs and its most complete is eight rakahs and its middle is four or six rakahs, and the encouragement to maintain it
Numbering
Darussalam 1662
Muslim 1662