(78) باب بَيْعِ الْفِضَّةِ بِالْفِضَّةِ
Narrated Abu Sa`id Al-Khudri:
Allah's Messenger (ﷺ) said, "Do not sell gold for gold unless equivalent in weight, and do not sell less amount for greater amount or vice versa; and do not sell silver for silver unless equivalent in weight, and do not sell less amount for greater amount or vice versa and do not sell gold or silver that is not present at the moment of exchange for gold or silver that is present.
Reference: Sahih al-Bukhari 2177
In-book reference: Book 34, Hadith 127
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 3, Book 34, Hadith 385