بُلُوغُ الْمَرَامِ
Bulugh al-Maram 837
Business Transactions
وَعَنْ مَعْمَرِ بْنِ عَبْدِ اَللَّهِ - رضى الله عنه - قَالَ: إِنِّي كُنْتُ أَسْمَعُ رَسُولَ اَللَّهِ - صلى الله عليه وسلم -يَقُولُ: { اَلطَّعَامُ بِالطَّعَامِ مِثْلاً بِمِثْلٍ " وَكَانَ طَعَامُنَا يَوْمَئِذٍ اَلشَّعِيرَ } رَوَاهُ مُسْلِمٌ [1] .
Narrated Ma'mar bin 'Abdullah (RA): I used to hear Allah's Messenger (ﷺ) say, "Food (may be sold) for food, of same quantities." Our food at that time consisted of barley. [Reported by Muslim].
Sunnah.com reference: Book 7, Hadith 71