What does Mark 3:12 mean?

Jesus is on the shore of the Sea of Galilee, swarmed by people from all over the region and beyond who want to touch Him to be healed (Mark 3:7–10). In that mob are those who are possessed by demons. The demons know who He is and have no choice but to fall to the ground and worship Him. But He will not allow them to testify to the people about His true identity. There are a couple of reasons for this.

The God of the Bible is the God who works in history. At this point, He has influenced history for thousands of years, preparing the people and the culture for the arrival of His Son. During Jesus' ministry, He works strategically to reveal who Jesus is and what He's come to do. Whether intentionally or unintentionally, the demon's apparent compulsion to declare Jesus the Son of God works against God's plans, so Jesus silences them.

Another reason ties into Satan's title as the "father of lies" (John 8:44). One of Satan's greatest talents is taking a truth and adding just enough deception to make it dangerous. If Jesus validates the demons as witnesses to His identity, they'll assume the authority to tell people more about Jesus—and lie about Him. This would make their message even more dangerous than that of the Pharisees who should know Jesus as the Messiah, but blind themselves to the truth.

Then, as now, Jesus wants His followers to bear witness to Him—Who He is, and what He does in our lives. That is why He commissions His followers to "Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe all that I have commanded you…" (Matthew 28:19–20).