Spoken by the prophet Jeremiah (vs 9)

As to Matt. 27:9, which makes Jeremiah say something that is only to be found in Zecchariah, it is credibly testified (Sir Isaac Newton), that several of the chapters in Zechariah are transposed from Isaiah or Jeremiah. The verse in question shows that it was Jeremiah.
1880 The Christadelphian: Volume 17. p 572

“Jeremy” or Zechariah (Matt. 27:9)
‎Answer.—There is no question about the reading in Matthew; but it will be observed that the citation is of that which was “spoken” by (or through—R.V., marg.) Jeremiah the prophet. It does not say “written” by him.

...Mede thought it very probable that the 9th, 10th and 11th chapters of Zechariah were written in the first instance by Jeremiah. Now, it is in the last of these chapters that we find the words quoted by St. Matthew. That evangelist, therefore, could quote them as those of Jeremiah, in like manner as the apostle Jude has quoted as those of Enoch the words of his 14th and 15th verses.
1926 Christadelphian p 405

( non Berean)
‎The prophecy is cited as fulfilled in the circumstances of the crucifixion by Matthew in chapter 27:9–10; but he refers it to Jeremiah. A charge has been made that Matthew incorrectly ascribes the words of Zechariah to Jeremiah. McCaul quotes various suggested explanations, but favours the view that Matthew intentionally ascribed the words of Zechariah to Jeremiah, because he wished to impress upon his readers the fact that Zechariah’s prediction was a reiteration of two fearful prophecies of Jeremiah (Jer. 18, 19), and should, like them, be accomplished in the rejection and destruction of the Jewish people. “He wished to remind them that ‘The field of blood’, purchased with the money that testified the fulness of their guilt, was a part of that valley of the son of Hinnom, which their fathers had made a ‘field of blood’ before them, and where Jeremiah had twice, by the symbol of a potter’s vessel, announced their coming destruction. The words of the prophet, ‘Cast it to the potter’, were in themselves sufficient to direct the attention of readers acquainted with the prophecies, to those two chapters of Jeremiah; but the manner in which Matthew introduces his quotation, makes the allusion still more plain. He first relates the purchase of the potter’s field, thereby pointing out the locality of Jeremiah’s prophecy—then he mentions the fact that it was called ‘the field of blood’, thereby referring to a very similar expression in that prophet; ‘Behold the days come, saith the Lord, that his place shall no more be called Tophet, nor the valley of the son of Hinnom, but The valley of slaughter’ (Jer. 19 : 6); and then cites the words of Zechariah as spoken by Jeremiah, in order to make all mistake impossible. Matthew had, therefore, a direct purpose in introducing the name of Jeremiah; it was to warn the Jews against the coming judgments. They fondly hoped that, as the chosen people of God, they were safe. Matthew points them to the potter’s field, and thus reminds them of the calamities which had already come upon them for past sin, less heinous than that of which the potter’s field now testified.”
1964 The Christadelphian: Volume 101. 2001 (electronic ed.) (447–448).