Riyad as-SalihinChapter 4Hadith 143
Full Sharh — Riyad as-Salihin 143
وعن قيلة بنت مخرمة رضى الله عنها قالت: رأيت النبي صلى الله عليه وسلم وهو قاعد القرفصاء، فلما رأيت رسول الله صلى الله عليه وسلم المتخشع في الجلسة أرعدت من الفرق. ((رواه أبو داود والترمذي)).
English Translation
Qailah bint Makhramah (May Allah be pleased with her) reported:: I saw the Prophet (ﷺ) seated with his arms enfolding his legs; and when I saw him in such a state of humble guise I trembled with fear due to the awe (he showed in that posture)..
Source
Riyad as-Salihin(رياض الصالحين)
The Book of the Etiquette of Sleeping, Lying and Sitting etc
Hadith Number
143