Thought from Today's Old Testament Passage:
[Jeremiah 18] Verses 1-10. The prophet is here sent to the potter's house (he knew where to find it), not to preach a sermon as before to the gates of Jerusalem, but to prepare a sermon, or rather to receive it ready prepared.... "Go to the potter's house, and observe how he manages his work, and there I will cause thee, by silent whispers, to hear my words. There thou shalt receive a message, to be delivered to the people." Note, Those that would know God's mind must observe his appointments, and attend where they may hear his words. The prophet was never disobedient to the heavenly vision, and therefore went to the potter's house (v. 3) and took notice how he wrought his work upon the wheels, just as he pleased, with a great deal of ease, and in a little time. And (v. 4) when a lump of clay that he designed to form into one shape either proved too stiff, or had a stone in it, or some way or other came to be marred in his hand, he presently turned it into another shape; if it will not serve for a vessel of honour, it will serve for a vessel of dishonour, just as seems good to the potter. It is probable that Jeremiah knew well enough how the potter wrought his work, and how easily he threw it into what form he pleased; but he must go and observe it now, that, having the idea of it fresh in his mind, he might the more readily and distinctly apprehend that truth which God designed thereby to represent to him, and might the more intelligently explain it to the people.
Matthew Henry, Matthew Henry's Commentary on the Bible (Peabody, MA: Hendrickson Publishers) 1997.