(36) باب اشْتِرَاءِ التَّمْرِ بِالرُّطَبِ
it was narrated that Sa'd said:
"The Messenger of Allah was asked about (buying) fresh dates with dried dates, and he said to those who were around him: 'Will fresh dates decrease (in weight or volume) when they dry out?" they said Yes,' so he forbade that." (ES)
Reference (ES): Sunan an-Nasa'i 4545 (ES)
In-book reference (ES): Book 44, Hadith 97 (ES)
English translation (ES): Vol. 5, Book 44, Hadith 4549 (ES)