Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) says that the Prophet (peace and blessings be upon him) "forbade two sales and two kinds of dress. The two sales are al-mulamasah and al-munabadhah, and the two kinds of dress are ishtimal al-samma' and a man sitting wrapped in his garment with his knees drawn up in such a way that his private parts are exposed."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10870