When Judas, who betrayed Jesus, saw that Jesus was condemned to die, he felt deep regret. He returned the thirty pieces of silver to the chief priests and elders, and
References for Matthew 27:3
said, "I did wrong because I betrayed an innocent man." But they said, "What is that to us? That's your problem."
Judas threw the silver pieces into the temple and left. Then he went and hanged himself.
The chief priests picked up the silver pieces and said, "According to the Law it's not right to put this money in the treasury. Since it was used to pay for someone's life, it's unclean."
So they decided to use it to buy the potter's field where strangers could be buried.
That's why that field is called "Field of Blood" to this very day.
This fulfilled the words of Jeremiah the prophet: And I took the thirty pieces of silver, the price for the one whose price had been set by some of the Israelites,
and I gave them for the potter's field, as the Lord commanded me.
References for Matthew 27:10