The Messenger of Allah ﷺ used to perform witr with thirteen rakahs. When he grew older and weaker, he performed witr with nine. Umara bin Umayr differed with him and reported it from Yahya bin Jazzar from Ayesha.
أخبرنا أحمد بن حرب قال حدثنا أبو معاوية عن الأعمش عن عمرو بن مرة عن يحيى بن الجزار
كان رسول الله ﷺ يوتر بثلاث عشرة ركعة فلما كبر وضعف أوتر بتسع خالفه عمارة بن عمير فرواه عن يحيى بن الجزار عن عائشة
Sahih. Tirmidhi transmitted it in the Book of Prayer, chapter on what has been said about Witr with seven, hadith no. 457, from the hadith of Abu Muawiya Dareer, and he said, "Hasan," and the hadith has many corroborating witnesses.