What does Mark 4:9 mean?

This verse acts as the matching bookend to the introduction of the parable, as begun in verse 3. Jesus starts with the command to listen, and ends with the command to hear. To "listen" is to make the effort to catch the words of the speaker; to "hear" is to have the words in hand so you can analyze the message.

The wording of this verse infers that some can accept Jesus' words while others can't, but this "deafness" may be partial and/or temporary. As human beings, we often ignore the Bible if it tells us what we don't want to hear about a certain topic, such as sex. Peter had issues with accepting Gentiles into Jesus' family. After a very graphic vision (Acts 10:9–16) and firsthand proof that God gives the Holy Spirit to non-Jews (Acts 10:34, 44), he still had a hard time completely accepting them into the church (Galatians 2:11–14).

For others, this spiritual deafness is more complete, but temporary. Paul's conversion is probably the most dramatic (Acts 9), but priests (Acts 6:7), Pharisees, and Jesus' own brothers (Acts 1:14) also came to accept Him as their savior. This is one reason why we should spread the gospel liberally. Someone may not be listening in the moment, but the words could bear fruit in the future.

We choose whether to hear, but we also choose how much to hear. Mark 4:24–25 explains that we determine how big the "measure"—meaning the container—we want filled with Jesus' words. We decide how much of the truth we want to hear and accept. Jesus understands that His message is a lot to take in. He gives us truth as we are able to accept it (Mark 4:33). As we learn more about Him and have more faith in Him, we should naturally see our ability to accept His words grow. If we find ourselves in a place of unbelief, it may be that we are caught up in the rocky ground of persecution or the choking thorns of consumerism. We need to evaluate our lives to see what sin and distractions are keeping us from hearing what Jesus has to say.