John Calvin Commentary Jeremiah 3:9

"And it came to pass through the lightness of her whoredom, that the land was polluted, and she committed adultery with stones and with stocks." — Jeremiah 3:9 (ASV)

Here the Prophet completes his charge: the punishment God inflicted on the Israelites had so little effect on the tribe of Judah that she surpassed her sister's harlotries with her own levity and lustfulness. He says, She has polluted the land, or caused the land to sin—that is, made the land guilty. Indeed, it strongly highlights the crime when it is said that the land became guilty or contaminated. The land, we know, was in itself pure and could contract no pollution from the vices of people; but to show their impiety as more detestable, the land is said to have been contaminated by them.

Alternatively, it may be said that the land was made guilty. How so? The reason they are said to have contaminated the land, made it guilty, or implicated it in their own vices, he gives in these words: she has played the harlot with stone and with wood. We do not need to elaborate now on this metaphor of playing the harlot, for we have already said that this analogy is often repeated because God had united that people to Himself and bound them to Him, as it were, by the sacred bond of marriage. Therefore, whenever the people departed from the pure worship of God, they were justly said to have played the harlot, for they violated their pledged faith. Just as sincere faith is spiritual chastity, so apostasy is the shamelessness and treachery shown when a wife becomes unfaithful to her husband by following adulterers.