بُلُوغُ الْمَرَامِ
Bulugh al-Maram 301
The Book of Prayer
وَعَنْ عَائِشَةَ -رَضِيَ اَللَّهُ عَنْهَا- قَالَتْ : { رَأَيْتُ رَسُولَ اَللَّهِ - صلى الله عليه وسلم -يُصَلِّي مُتَرَبِّعًا } رَوَاهُ النَّسَائِيُّ , وَصَحَّحَهُ اِبْنُ خُزَيْمَةَ . [1]
Narrated 'Aishah (RA): I saw Allah's Messenger (ﷺ) praying while he sat cross-legged. [Reported by an-Nasa'i, and Ibn Khuzaimah graded it Sahib (authentic)].
Sunnah.com reference: Book 2, Hadith 187