Language:
كتاب البيوع
34  
Sales and Trade
(64)
Chapter: The seller is not allowed to keep animal unmilked for a long time
(64)
باب النَّهْىِ لِلْبَائِعِ أَنْ لاَ يُحَفِّلَ الإِبِلَ وَالْبَقَرَ وَالْغَنَمَ وَكُلَّ مُحَفَّلَة
Sahih al-Bukhari 2149

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 (ﷺ) 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.‏
Reference : Sahih al-Bukhari 2149
In-book reference : Book 34, Hadith 101
USC-MSA web (English) reference : Vol. 3, Book 34, Hadith 359
  (deprecated numbering scheme)