If a ruler listens to falsehood,
all his officials will be wicked.
One of the common sense rules of economics is that supply often follows demand. When, for example, the iPhone created a huge demand for smartphones, dozens of others manufacturers attempted to fill the market with a supply of smartphones of varying quality. That same principle is the point of today's proverb: if a ruler creates a demand for falsehood with his listening ear, he will find himself surrounded by wicked people willing to flood the market with even more lies.
Many of the wicked kings of Israel and Judah were also the victims of wicked advisors. King Ahab, for instance, was led into wickedness and idolotry by his wife Jezebel (see 1 Kings 19). Readers of The Lord of the Rings might be reminded of Théoden, king of Rohan, a once powerful leader who was unwilling to confront the threat of Sauron. Because he would not face reality, he fell more and more under the sway of his wicked advisor, Wormtongue (an apt name for the wicked officials of this proverb!). Only supernatural intervention saved Théoden (and you should read the whole trilogy until you get to this wonderful scene, and then keep going).
This proverb reminds us to pray for our leaders, both in civil government and in the church. More specifically, we should pray that our leaders might be people of character and virtue who will give no opportunity for wicked officials. Leadership is often a lonely calling that is subject to many temptations, not least from wicked advisors. Our leaders need wisdom from God! Let us also give thanks for godly leaders who, by God's grace, create atmospheres of truth-telling and cultuvate character that attracts righteous advisors. What a great mercy that, even in a fallen and sinful world, God has given his church—and even the wider world—many such leaders.