Ya'la bin Shaddad bin Aws said: I was present with Sayyiduna Mu'awiyah (may Allah be pleased with him) in Bayt al-Maqdis, and he led us in the Friday prayer. I looked, and most of those in the mosque were Companions of the Messenger of Allah (peace and blessings be upon him) (may Allah be pleased with them). I saw that they were sitting with their knees drawn up (ihtiba') while the imam was delivering the sermon. (b) Imam Abu Dawud (may Allah have mercy on him) said: Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) used to sit with his knees drawn up during the sermon, and Sayyiduna Anas bin Malik (may Allah be pleased with him), Shurayh (may Allah have mercy on him) and others did not consider there to be any harm in it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجمعة / 5910