(2) باب السَّلَمِ فِي وَزْنٍ مَعْلُومٍ
Narrated Ibn `Abbas:
The Prophet (ﷺ) came (to Medina) and he told the people (regarding the payment of money in advance that they should pay it) for a known specified measure and a known specified weight and a known specified period.
Reference: Sahih al-Bukhari 2241
In-book reference: Book 35, Hadith 5
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 3, Book 35, Hadith 445