What does Proverbs 4:20 mean?

Asking someone to "incline [their] ear" brings up the image of someone leaning forward, tipping their head to hear more clearly. The point is that these words are not to be passively taken in, but actively and carefully considered. Simply hearing wise counsel is inadequate unless the listener pays close attention to it. This corresponds to many other verses in Proverbs which encourage valuing godly wisdom.

Jesus cautioned, "Pay attention to what you hear" (Mark 4:24). He had concluded a discourse about the kinds of soil on which seed fell. The seed that fell along a path represents the Word that Satan quickly removes (Mark 4:15). The seed sown on rocky ground represents the Word that hearers receive joyfully but discard when persecution strikes them (Mark 4:16–17). The seed sown among thorns represents the Word that others receive until worldly concerns, the deceitfulness of riches, and materialistic desires choke it (Mark 4:18–19). The seed that fell on good soil represents the Word that hearers accept and show how well they accept it by bearing fruit in their lives. (Mark 4:20). It is important, therefore, to welcome God's Word with open ears and an open heart.