What were the postures of the Prophet (peace be upon him) while sitting during prayer and outside of it, in his home and with his Companions, and where did he place his hands outside of prayer or when conversing with his Companions and wives?

The Prophet's (PBUH) Sunnah sittings during the Tashahhud are three: Iftirash, which is for the first Tashahhud; Tawarruk, which is for the last Tashahhud; and Iqa', which is occasionally between the two prostrations. As for Tarrabbu (sitting cross-legged), scholars have differed concerning it. Ibn Abd al-Barr said: "It is not permissible to sit cross-legged in a fard (obligatory) prayer except for a sick person." Ibn Abi Shaybah narrated from Ibn Masud who said: "That I sit cross-legged on two hot stones is dearer to me than that I sit cross-legged in prayer." As for his sittings outside of prayer, it is reported that he would sometimes sit ihtiba' (sitting on one's buttocks with knees raised and arms wrapped around them) and sometimes cross-legged. He (PBUH) forbade the sitting of those upon whom is wrath (which is to place one's left hand behind one's back and lean on the palm of one's hand). Scholars have explicitly stated that it is permissible to sit in any posture as long as it does not result in something forbidden, such as uncovering one's awrah (private parts) or extending one's leg in front of people. As for placing one's hand outside of prayer, nothing specific has been reported concerning it, and there is latitude in the matter.