(13) باب اسْتِحْبَابِ صَلاَةِ الضُّحَى وَأَنَّ أَقَلَّهَا رَكْعَتَانِ وَأَكْمَلَهَا ثَمَانِ رَكَعَاتٍ وَأَوْسَطَهَا أَرْبَعُ رَكَعَاتٍ أَوْ سِتٌّ وَالْحَثِّ عَلَى الْمُحَافَظَةِ عَلَيْهَا
Abu Murra narrated on the authority of Umm Hani that the Messenger of Allah (ﷺ) on the day of the Conquest of Mecca observed in her house eight rak'ahs of prayer in one cloth, its opposite corners having been tied from the opposite sides.
Reference: Sahih Muslim 336 g
In-book reference: Book 6, Hadith 100
USC-MSA web (English) reference(deprecated numbering scheme): Book 4, Hadith 1556