(13) باب اسْتِحْبَابِ صَلاَةِ الضُّحَى وَأَنَّ أَقَلَّهَا رَكْعَتَانِ وَأَكْمَلَهَا ثَمَانِ رَكَعَاتٍ وَأَوْسَطَهَا أَرْبَعُ رَكَعَاتٍ أَوْ سِتٌّ وَالْحَثِّ عَلَى الْمُحَافَظَةِ عَلَيْهَا
Abu Huraira reported:
My friend Abu'l-Qasim (ﷺ) instructed me to do three things, and the rest of the hadith is the same. (ID)
Reference (ID): Sahih Muslim 721 c (ID)
In-book reference (ID): Book 6, Hadith 104 (ID)
USC-MSA web (English) reference(deprecated numbering scheme): Book 4, Hadith 1560 (ID)