The Book of Legal Punishments
حَدَّثَنَا يَحْيَى بْنُ يَحْيَى، قَالَ قَرَأْتُ عَلَى مَالِكٍ عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَطَعَ سَارِقًا فِي مِجَنٍّ قِيمَتُهُ ثَلاَثَةُ دَرَاهِمَ .Ibn 'Umar reported that Allah's Messenger (may peace upon him) cut off the hand of a thief (in case of the theft) of a shield the price of which was three dirhams
From Sahih Muslim, whose reports the scholars accept as authentic.