Ayesha reported,

Mother of the Believers, give me a ruling about the witr prayer of the Messenger of Allah ﷺ.She replied, "We used to prepare his toothstick and his water for purification, and Allah would rouse him at whatever hour of the night He willed. He would brush his teeth, perform ablution, then pray nine units of prayer, not sitting in any of them except at the eighth. There he would call upon his Lord, remember Allah, praise Him, and supplicate. Then he would rise without giving the closing salam, stand and pray the ninth unit, then sit and remember Allah, praise Him, supplicate his Lord, and send blessings upon His Prophet. Then he would give the salam aloud so that we could hear him. After that he would pray two more units while sitting, after the salam, making eleven units in total.When the Messenger of Allah ﷺ grew older and his body became heavier, he would pray witr with seven units and then pray two units while sitting after the salam."

حدثنا أبو بكر بن أبي شيبة حدثنا محمد بن بشر حدثنا سعيد بن أبي عروبة عن قتادة عن زرارة بن أوفى عن سعد بن هشام قال

سألت عائشة قلت

يا أم المؤمنين أفتيني عن وتر رسول الله ﷺ قالت كنا نعد له سواكه وطهوره فيبعثه الله فيما شاء أن يبعثه من الليل فيتسوك ويتوضأ ثم يصلي تسع ركعات لا يجلس فيها إلا عند الثامنة فيدعو ربه فيذكر الله ويحمده ويدعوه ثم ينهض ولا يسلم ثم يقوم فيصلي التاسعة ثم يقعد فيذكر الله ويحمده ويدعو ربه ويصلي على نبيه ثم يسلم تسليما يسمعنا ثم يصلي ركعتين بعد ما يسلم وهو قاعد فتلك إحدى عشرة ركعة فلما أسن رسول الله ﷺ وأخذ اللحم أوتر بسبع وصلى ركعتين بعد ما سلم