Wa alaykum salam wa rahmatuLlahi wa barakatuHu,

It is related on the authority of Zubayr b. al-‘Awwam that,

كان رسول الله صلى الله عليه وسلم إذا قعد يدعو وضع يده اليمنى على فخذه اليمنى ويده اليسرى على فخذه اليسرى وأشار بإصبعه السبابة ووضع إبهامه على إصبعه الوسطى ويلقم كفه اليسرى ركبته

“The Prophet Muhammad would, when he sat supplicating [tashahhud, etc], place his left hand on his left thigh and his right hand on his right thigh. He would point with his index finger, and place his thumb on his middle finger. His left hand would cover his knee.” (Sahih Muslim v. 5, p. 828)

Thus, “his left hand would cover his knee” is evidence for what is recommended [mustahabb]. In fact, the scholars agree that it is recommended for one to place the hand near to the knee or on the knee. (Sharh Sahih Muslim v. 5, p. 829) Also, on the authority of Ibn ‘Umar the wording is found,

ووضع يده اليمنى على ركبته اليمنى

“And he placed his right hand on his right knee.” (Sahih Muslim v. 5, p. 828)

Furthermore, regarding the right, Imam Nawawi stated,

فيضعها علي طرف الركبة اليمني

“Then, he should place it on the edge of the knee.” (Sharh al-Muhadhdhab v. 3, p. 433)

And Allah knows best.

Shafiifiqh.com Fatwa Dept.