Musnad Ahmad 33:66

Hajjaj and Rawh narrated to us, from Ibn Jurayj, Abu al-Zubayr informed me that he heard Jabir say: The Messenger of Allah (ﷺ) said: "Do not walk in one sandal, and do not perform *ihtiba* (sitting with the knees drawn up to the chest) in a single garment, and do not eat with your left hand, and do not wrap yourself in the *al-samma'* style, and do not place one of your legs over the other while lying on your back." I said to Abu al-Zubayr: "Is it placing his leg on the knee while lying on his back?" He said: "Yes." He said: "As for *al-samma'*, it is one of the ways of dressing, where you place the inner part of your garment and its outer part over one of your shoulders." I said to Abu al-Zubayr: "For they say: 'Do not perform *ihtiba* in a single garment while being exposed (i.e., with nothing underneath).'" He said: "That is how I heard Jabir say: 'Do not perform *ihtiba* in a single garment.'" Hajjaj said, from Ibn Jurayj, 'Amr said to me: "While being exposed."