It is narrated from Sayyiduna Abu Layla (may Allah be pleased with him) that the Prophet of Allah (peace and blessings be upon him) said: "Whoever buys a she-camel whose udder was tied up (to retain milk) before the sale, then if he dislikes her, let him return her along with a sa' of dates."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6387