Sunan an-Nasa'i, Book 14, Hadith 1426 (In-Book) ⓘ
It was narrated that Jabir bin Samurah said: "I sat with the Prophet and I did not see him deliver the khutbah except standing, and he sat, then he stood up and delivered the second khutbah."
أَخْبَرَنَا عَلِيُّ بْنُ حُجْرٍ، قَالَ حَدَّثَنَا شَرِيكٌ، عَنْ سِمَاكٍ، عَنْ جَابِرِ بْنِ سَمُرَةَ، قَالَ جَالَسْتُ النَّبِيَّ صلى الله عليه وسلم فَمَا رَأَيْتُهُ يَخْطُبُ إِلاَّ قَائِمًا وَيَجْلِسُ ثُمَّ يَقُومُ فَيَخْطُبُ الْخُطْبَةَ الآخِرَةَ .
also referenced under: Volume 2, Book 14, Hadith 1416 (DarusSalam)