Narrated Ibn Mas'ud (RA):

If anyone buys a goat whose udder has been tied up and he returned it, he must return it with one Sa'. [Reported by al-Bukhari].

وَعَنِ اِبْنِ مَسْعُودٍ ‏- رضى الله عنه ‏- قَالَ: { مَنِ اِشْتَرَى شَاةً مَحَفَّلَةً, فَرَدَّهَا, فَلْيَرُدَّ مَعَهَا صَاعًا } رَوَاهُ اَلْبُخَارِيُّ [1]‏ .‏