It is not lawful for to put them into the treasury. — The Greek for the last word is the Corban, or sacred treasure-chest of the Temple, into which no foreign coins were admitted, and from which the Law (Deuteronomy 23:18) excluded the unclean offerings of the price of shame, which entered largely into the ritual of many heathen nations. By parity of reasoning, the priests seem to have thought that the blood-money which was thus returned was excluded also.
Related Commentaries of Matthew 27:6
Matthew 27:6
6 And the chief priests took the silver pieces, and said, It is not lawful for to put them into the treasury, because it is the price of blood.