Sunan an-Nasa'i, Volume 2, Book 14, Hadith 1417 (DarusSalam) ⓘ
It was narrated from 'Abdullah that: The Messenger of Allah used to deliver two khutbahs standing, and he would separate them by sitting.
أَخْبَرَنَا إِسْمَاعِيلُ بْنُ مَسْعُودٍ، قَالَ حَدَّثَنَا بِشْرُ بْنُ الْمُفَضَّلِ، قَالَ حَدَّثَنَا عُبَيْدُ اللَّهِ، عَنْ نَافِعٍ، عَنْ عَبْدِ اللَّهِ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَانَ يَخْطُبُ الْخُطْبَتَيْنِ وَهُوَ قَائِمٌ وَكَانَ يَفْصِلُ بَيْنَهُمَا بِجُلُوسٍ .
also referenced under: Book 14, Hadith 1427 (In-Book)