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
I saw the Prophet (sallallahu alayhi wa sallam) 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).
Riyad as-Salihin 822, Book 5, The Book of the Etiquette of Sleeping, Lying and Sitting etc, Hadith 10. 1 min read