Jamieson, Fausset and Brown on Jeremiah 18:6

6. Refuting the Jews' reliance on their external privileges as God's elect people, as if God could never cast them off. But if the potter, a mere creature, has power to throw away a marred vessel and raise up other clay from the ground, a fortiori God, the Creator, can cast away the people who prove unfaithful to His election and can raise others in their stead (compare Is 45:9; 64:8; Ro 9:20, 21). It is curious that the potter's field should have been the purchase made with the price of Judas' treachery (Mt 27:9, 10: a potter's vessel dashed to pieces, compare Psa 2:8, 9; Re 2:27), because of its failing to answer the maker's design, being the very image to depict God's sovereign power to give reprobates to destruction, not by caprice, but in the exercise of His righteous judgment. Matthew quotes Zechariah's words (Zec 11:12, 13) as Jeremiah's because the latter (Jr 18:1-19:15) was the source from which the former derived his summary in Zec 11:12, 13 [Hengstenberg].