It is possible that these chapters belong together. Yahweh's sovereignty over Judah and over the life of the prophet is the major theme that connects the various oracles together.
The message that Jeremiah receives (18:5-12) at the potter's house contains the theology of 18:1-12. Vv. 2-4 provide us with the illustration of “the free agency of man” and “the goodness and supremacy of God” over Israel and the nations (Clarke, 304). Corruption is the inherent characteristic of all humankind. It is the corruption of the clay (i.e., the moral corruption of Israel) that caused the pot to be marred (v. 4a). The reshaping of the clay to another pot (v. 4b), rather than discarding it as worthless to the potter, shows Yahweh's willingness to extend grace to those who are under his judgment (v. 6). The offer of grace is made to all who repent of their sins and demonstrate their willingness to conform to his will (vv. 7-8). The universality of God's saving grace is clearly evident here. Those who enjoy his salvation, if they become corrupt again, face the judgment of God (vv. 9-10). Obedience is the necessary condition, not only for the initial experience of salvation, but also for its continued enjoyment.
Judgment is upon the covenant people who failed to show constancy and dependability in their relationship with Yahweh (18:13-17). These are qualities found in nature, even in the most unlikely places (v. 14). Judah's forgetfulness of their God is a horrible sin (see 2:9-13). On the day of judgment, those who reject God cannot expect to experience anything but rejection by Yahweh.
In 18:18 the people plot to slander Jeremiah as a false prophet. Those who trust the words of corrupt, complacent, and irresponsible religious leaders regard Yahweh's true spokesman as an obstacle that should be removed. Jeremiah makes another “confession” in 18:19-23. His prayer for the destruction of his enemies should be evaluated in the light of other admonitions that call for a more honorable way to treat one's enemy (Pr 25:21-22; see Mt 5:38-48; Ro 12:19ff.).
Yahweh's determination to destroy Jerusalem is the direct consequence of the blatant sins of its inhabitants (19:1-13). The city and its people are like a clay jar, designed and fashioned by a potter. The potter (Yahweh) finds his vessel unusable for any purpose. Therefore he has no other choice but to destroy it irreparably. An apostate people is a useless people for God. The divine decision is to bring them to their end. The place of worship (Jerusalem) that they have abandoned will be destroyed; the place of worship that they have chosen for themselves (the valley of Ben Hinnom) will become their burial ground.
Yahweh's spokesman is not shaken by disciplinary action taken by leaders of the established religion (19:14-20:6). His call is to preach judgment and that he must preach regardless of what others may think or what actions may be taken against him. He is convinced that in the end the false leaders will suffer shame for corrupting and lying to the people.
The man of God, however, is also a human being who cannot escape his own emotions and feelings (20:7-12). His unpopularity compels him to think that his call was a deception used by God to exercise his sovereign will over his feeble nature (v. 7). At the same time, he is also aware of the terrible consequences of his refusal to speak Yahweh's word. Even in this darkest hour he is certain that Yahweh is his defender, who will not abandon those who commit their cause to him. The man of God in conflict can do only one thing—offer his praises to Yahweh who defends and sustains his servants with his grace (v. 13).
The lament of Jeremiah in 20:14-18 is much like Job's lament (Job 3). He feels nothing but anger toward God and his fellow human beings. It is a terrible task to be a messenger of doom. He must experience the painfulness of the divine wrath twice—when the word comes to him initially and when the word is realized in the history of his nation. The divine call came to Jeremiah at his birth. That moment is no longer a joyous occasion; his life is filled with trouble, sorrow, and shame. Though no divine response to this lament is forthcoming, the preceding hymn of praise suggests to us that in this loneliest hour, Yahweh did not abandon his faithful servant to despair and defeat.