Musannaf Ibn Abi Shayba 13:1446

Abu Bakr narrated to us, he said: Waki’ narrated to us, from Aslam, from Alqamah ibn Marthad, from Razin ibn Sulayman, from Sa’id ibn al-Musayyib, he said: There is no harm in a forward sale (salam) for garments, with a known measurement, for a known term.