Rest Sitting (Jalsat al-Istirāḥah):
Again, when you raised your head from the second prostration, you would sit briefly on your left leg just long enough for all the bones of the body to return to their proper positions.

حَدَّثَنَا مُحَمَّدُ بْنُ الصَّبَّاحِ ، ‏‏‏‏‏‏قَالَ:‏‏‏‏ أَخْبَرَنَا هُشَيْمٌ ، ‏‏‏‏‏‏قَالَ:‏‏‏‏
أَخْبَرَنَا خَالِدٌ الْحَذَّاءُ ، ‏‏‏‏‏‏عَنْ أَبِي قِلَابَةَ ، ‏‏‏‏‏‏قَالَ:‏‏‏‏
أَخْبَرَنَا مَالِكُ بْنُ الْحُوَيْرِثِ اللَّيْثِيُّ ، ‏‏‏‏‏‏أَنَّهُ رَأَى النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يُصَلِّي فَإِذَا كَانَ فِي وِتْرٍ مِنْ صَلَاتِهِ لَمْ يَنْهَضْ حَتَّى يَسْتَوِيَ قَاعِدًا.
Narrated Muhammad ibn al-Sabbah: He said, Hushaym informed us, saying:
Khalid al-Hadhdha’ informed us, from Abu Qilabah, who said: Malik ibn al-Huwayrith al-Laythi informed us that he saw the Prophet (may Allah bless him and give him peace) praying, and when he was in an odd-numbered rak‘ah of his prayer, he would not rise until he had sat up straight.
(Sahih al-Bukhari, Hadith 823)
Again, the Prophet (may Allah bless him and give him peace) would, for the second rak‘ah, support himself on the ground with both his hands when rising. And when you stood up, you would clench both your fists and lean on them to rise.