John Calvin on Jeremiah 23:38

Here the Prophet confirms what he had said, for God might have seemed to be too indignant, having been so grievously offended at one short expression. The Jews had borrowed from the prophets themselves, when they called prophecies burdens, as we have already said, and as we find in many places. Now as the lubricity of language is great, though the Jews might have done wrong as to one word, it might yet have appeared an insufficient reason for the punishment which God threatened to inflict. But the Prophet here shews that God was justly angry with them, for he had sent to them, and often warned them not to use this form of speaking, which was a manifest evidence of their impiety. As then they had thus disregarded God and his warnings, was it an excusable mistake? In short, Jeremiah shews that they had not erred inconsiderately, as it often happens as to those who speak rashly and thoughtlessly, but that this perverted way of speaking proceeded from determined wickedness, from a wish to affix some mark of disgrace to God’s word; and thus they acted in disdain towards God himself. This then is the import of the words.