"Then was fulfilled that which was spoken by Jeremy the prophet, saying, And they took the thirty pieces of silver, the price of him that was valued, whom they of the children of Israel did value; And gave them for the potter's field, as the Lord appointed me." (Matthew 27:9-10, KJV)
Critics say this prophecy was not by Jeremy (Jeremiah) but by Zechariah. Zechariah 11:12-13 says:
"And I said unto them, If ye think good, give me my price; and if not, forbear. So they weighed for my price thirty pieces of silver. And the LORD said unto me, Cast it unto the potter: a goodly price that I was prised at of them. And I took the thirty pieces of silver, and cast them to the potter in the house of the LORD." (Zechariah 11:12-13)
The words from Zechariah 11:12-13 are not the exact words recorded at Matthew 27:9-10. Zechariah does not mention the "children of Israel" and the "field". In fact, only Jeremiah mentions the "field". Jeremiah 32:6-10 describes Jeremiah being commanded by the LORD to buy a field with seventeen shekels of silver. It says:
"And Jeremiah said, The word of the LORD came unto me, saying, Behold, Hanameel the son of Shallum thine uncle shall come unto thee, saying, Buy thee my field that is in Anathoth: for the right of redemption is thine to buy it. So Hanameel mine uncle's son came to me in the court of the prison according to the word of the LORD, and said unto me, Buy my field, I pray thee, that is in Anathoth, which is in the country of Benjamin: for the right of inheritance is thine, and the redemption is thine; buy it for thyself. Then I knew that this was the word of the LORD. And I bought the field of Hanameel my uncle's son, that was in Anathoth, and weighed him the money, even seventeen shekels of silver. And I subscribed the evidence, and sealed it, and took witnesses, and weighed him the money in the balances." (Jeremiah 32:6-10)
The text does not say how many pieces of silver in Jeremiah's day amounted to this seventeen shekels of silver. The amount may have equaled thirty pieces of silver. In any case, since only Jeremiah refers to a God-appointed purchase of a field, the reference to Jeremiah at Matthew 27:9-10 is certainly intentional and not a scribal error. The text of Matthew 27:9-10 says "that which was spoken", not "that which was written", so there is no need to look for the exact quotation in the book of Jeremiah. Jeremiah spoke the prophecy but did not write it. Zechariah then wrote Jeremiah's oral prophecy while omitting the reference to a field because that detail had already been described in Jeremiah 32:6-10.