Sunan an-Nasa'i, Hadith 4948 ⓘ
It was narrated that Ayman bin Umm Ayman who attributed it to the Prophet said: "The (hand of) a thief is not to be cut off except for the price of a shield, and in those days the price of a shield was a Dinar."
أَخْبَرَنَا عَلِيُّ بْنُ حُجْرٍ، قَالَ أَنْبَأَنَا شَرِيكٌ، عَنْ مَنْصُورٍ، عَنْ عَطَاءٍ، وَمُجَاهِدٍ، عَنْ أَيْمَنَ بْنِ أُمِّ أَيْمَنَ، يَرْفَعُهُ قَالَ " لاَ تُقْطَعُ الْيَدُ إِلاَّ فِي ثَمَنِ الْمِجَنِّ " . وَثَمَنُهُ يَوْمَئِذٍ دِينَارٌ .
also referenced under: Book 46, Hadith 78 (In-Book) & Volume 5, Book 46, Hadith 4951 (DarusSalam)