The Prophet ﷺ used to pray nine units, sitting only during the eighth. In that sitting he would remember Allah, praise Him, and supplicate to Him, then rise without giving the closing salutation. He would then stand and pray the ninth unit, after which he would sit, remember Allah, praise Him, and supplicate to Him, then give the closing salutation loud enough for us to hear.
كان النبي ﷺ يصلي تسع ركعات، لا يجلس فيها إلا في الثامنة، فيذكر الله، ويحمده ويدعوه، ثم ينهض، ولا يسلم، ثم يقوم فيصلي التاسعة، ثم يقعد فيذكر الله، ويحمده، ويدعوه، ثم يسلم تسليما يسمعنا.
Muslim recorded it in Salat al-Musafirin (746) through the hadith of Qatada, from Zurara bin Awfa, from Saad bin Hisham bin Amir, from Ayesha, in a long hadith previously mentioned in full in the chapter gathering the Prophet's ﷺ night prayer.