The Prophet (may Allah’s peace and blessings be upon him) cut off (a thief's hand) for a shield that was worth three dirhams.

Allah, the Exalted, protected people’s lives, honor, and money through penalties that deter the aggressors. Hence, the penalty of the thief (who steals money or property from a place where it had been put away) is the amputation of the organ used to take the stolen property. This penalty atones the sin of the thief and deters others who might think of following such despicable ways to earn a living. Alternatively, such people would change their minds and try to make money in legitimate and modest ways. Ultimately, there would be more fruitful work, the world will be cultivated, and souls will be dignified.
In order to protect people’s properties and lives, maintain security, and encourage people to invest their money and make profits, Allah, the Exalted, out of His Wisdom, set a certain limit for the value of the stolen money or property, which is a quarter of a gold dinar. This is equal to one gram and one sixteenth of a gram, because the dinar weighs 4.25 grams.