The Messenger of Allah ﷺ used to pray nine rakahs during the night.
حدثنا محمد بن جعفر قال حدثنا شعبة عن أبي التياح قال سمعت سليمان بن مرثد أو مزيد يحدث
كان رسول الله ﷺ يصلي من الليل تسع ركعات
Its isnad is sahih. Sulayman bin Marthad, or Mazid, was deemed reliable by Ibn Hibban and accepted by others. Bukhari questioned his hearing from Ayesha, but Ibn Hajar responded to that, saying, "He explicitly stated that he heard from her." The hadith has already appeared at 24539.