What does Mark 4:23 mean?

This verse is a condensed summary of Mark chapter 4—an exhortation to pay attention to Jesus' words and strive to understand what He is teaching. It is also used in Mark 4:3 when He says, "Listen!" Mark 4:9 is an almost-direct quote. And Mark 4:24–25 expounds on the phrase.

The disciples who ask Jesus for clarification of His parables (Mark 4:10, 34) are the "good soil" of the parable of the sower (Mark 4:8, 20). They choose to stay near Jesus and ask Him the deeper truths of the parables He teaches the crowd. In return, Jesus chooses them for advanced training (Mark 3:13–19) so they can spread His message (Mark 6:7–13).

The word translated "ears" is from the Greek root word ous. Literally, it means the physical organs on the side of your head, but metaphorically, it means the spiritual capacity to understand what is taught. "Hear" is from the Greek root word akouo. Similarly to ous, the plain definition means to not be deaf, but it also means to attend to and perceive what is being said.

Having "ears to hear" isn't restricted to people who are well-educated, smart, or even wise. The Pharisees understand God's work in Israel better than anyone, yet they still don't take the time to contemplate the implications of Jesus' teaching. Conversely, as the gospel spreads, the disciples will come to realize that "anyone" includes Samaritans, Romans, Ethiopians—any Gentile who is willing to listen (Romans 1:16–17).

True understanding of Scripture comes only through the Holy Spirit (1 Corinthians 2:10–13), but we each have some say as to how much understanding we will accept (Mark 4:24–25, 33). Knowledge builds on knowledge, and understanding is tightly associated with obedience (John 5:39–40; 7:17). If we find ourselves in a season where we can't understand the Bible, it may be that we have rejected what God taught us previously, and He won't continue until we accept the earlier message. Listening and understanding involves a radical change of character. God is not interested in us being academics who understand the Bible but refuse to live it out.