According to Exodus 21:32, if an ox gored a neighbour’s slave to death, the owner was obligated to pay the neighbour thirty pieces of silver — that was the value of the dead slave. Thereafter, it became symbolic of contempt.
At one point in his ministry, the prophet Zechariah was asked to play a messianic role (Zechariah 11:4-14), meaning a role that the Messiah Himself would play in the future, the role of the good shepherd. For a period of time, Zechariah was to feed a flock destined for slaughter. He then was to approach the Jewish leaders and say that since they did not agree to a price in advance, they should pay him what they thought his labour was worth. If it was worth something, they should pay him accordingly; if it was worthless to them, it was acceptable to pay him nothing. To show their contempt for the prophet, the leaders deliberately chose to pay him thirty pieces of silver, conveying to Zechariah that his work among them was not only worthless but, more insultingly, was worth only the price of a dead slave. In verse 13 of the passage, God sarcastically said: “Throw it to the potter, that magnificent price at which I was valued by them!”
Zechariah prophesied that someday the Jewish leaders would sell out God Himself for the price of a dead slave. This was fulfilled in Matthew 26:14-16 when the chief priests deliberately chose thirty pieces of silver to show their contempt for Jesus; thus, they sold out the Messianic God-Man for the price of a dead slave.
As tragic as this is, ironically, the thirty pieces of silver came from the chief priests, so the money ultimately came from the Temple treasury. One major purpose of the Temple treasury was to purchase sacrifices. Though it was not their intent, the chief priests purchased a sacrifice, specifically, the final sacrifice for sin.