Sayyidah Maymunah (may Allah be pleased with her) narrates: When the Prophet (peace and blessings be upon him) sat (in the tashahhud), he would sit at rest on his left thigh.
Imam al-Tabarani recorded it in al-Mu'jam al-Kabir; its chain contains a narrator, Muhammad bin Sinan al-Qazzaz, whom Imam Abu Dawud and others declared a liar, while Imam al-Daraqutni (may Allah have mercy on him) declared him thiqah (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 2840