Imam Bukhari narrates: Qutaybah ibn Sa'id narrated to us, he said: Layth narrated to us, from Ibn Shihab, from 'Ubaydullah ibn 'Abdullah ibn 'Utbah, from Abu Sa'id al-Khudri (may Allāh be pleased with him), he says that

the Messenger of Allāh ﷺ forbade ishtimal-e-sammā and sitting in a single cloth in the manner of ihtibā, so that no part of the cloth remains upon the private part.