Narrated 'Abdullah bin Mas'ud:
Whoever buys a sheep which has not been milked for a long time, has the option of returning it along with one Sa of dates;
and the Prophet forbade going to meet the seller on the way (as he has no knowledge of the market price and he may sell his goods at a low price).
حَدَّثَنَا مُسَدَّدٌ، حَدَّثَنَا مُعْتَمِرٌ، قَالَ سَمِعْتُ أَبِي يَقُولُ، حَدَّثَنَا أَبُو عُثْمَانَ، عَنْ عَبْدِ اللَّهِ بْنِ مَسْعُودٍ ـ رضى الله عنه ـ قَالَ مَنِ اشْتَرَى شَاةً مُحَفَّلَةً، فَرَدَّهَا فَلْيَرُدَّ مَعَهَا صَاعًا. وَنَهَى النَّبِيُّ صلى الله عليه وسلم أَنْ تُلَقَّى الْبُيُوعُ.
• Sahih al-Bukhari, 2149
• Sahih al-Bukhari, Vol. 3, Book of Sales and Trade, Hadith 359
• Sahih al-Bukhari, Book of Sales and Trade, Hadith 359