I saw the Messenger of Allah ﷺ addressing the people at Mina (on the day of sacrifice) when the sun rose high (i.e. in the forenoon) on a white mule, and Ali (Allah be pleased with him) was interpreting on his behalf; some people were standing and some sitting.  

رَأَيْتُ رَسُولَ اللَّهِ ﷺ يَخْطُبُ النَّاسَ بِمِنًى حِينَ ارْتَفَعَ الضُّحَى عَلَى بَغْلَةٍ شَهْبَاءَ وَعَلِيٌّ ؓ يُعَبِّرُ عَنْهُ وَالنَّاسُ بَيْنَ قَاعِدٍ وَقَائِمٍ