Musannaf Ibn Abi Shayba 13:2535

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Isma’il ibn Muslim al-‘Abdi narrated to us, he said: Abu al-Mutawakkil al-Naji narrated to us, from Abu Sa’id al-Khudri, he said: The Messenger of Allah (may Allah bless him and grant him peace) said: Gold for gold, silver for silver, wheat for wheat, barley for barley, dates for dates, and salt for salt, like for like, hand to hand. Whoever increases or seeks an increase has committed usury (riba). The taker and the giver in it are equal.