What does Mark 3:25 mean?

Jesus is using the parable of a divided kingdom and a divided house to show that if He is using Satan's power to cast out demons, Satan's kingdom won't survive. Satan would gain no strategic value by allowing Jesus to use Satan's authority to attack his own work.

"Divided" is from the Greek root word merizo, which means to separate into component parts and distribute those parts. "Stand" is from the Greek root word histemi. It means to maintain authority and force, to keep whole. The word translated "house" refers to the members of the house—the family.

This phrase is better known in American culture for its use by President Abraham Lincoln during the U.S. Civil War. Lincoln's use pleaded for a united nation, rather than one bound for destruction through conflict. Jesus' intent, here, is to point out that it would be foolish for Satan to use his own power to interfere with demons.

Jesus' "house" can weather minor lapses in unity such as Judas' betrayal and Peter's denial. To be a serious threat, the rebelling authority needs to be on par with the leader of the house. That is, the members of the Trinity would have to work against each other. Jesus' attitude toward the Father prohibits this. He, "though he was in the form of God, did not count equality with God a thing to be grasped," (Philippians 2:6) and "humbled himself by becoming obedient to the point of death, even death on a cross" (Philippians 2:8).

But Jesus' family contains much more than just the Trinity. In Mark 3:34–35, Jesus explains that His family includes anyone who follows God. Paul talks about the inherent oneness of the church in Ephesians 4:1–6. The church is built on the unity of the Trinity and has "… one body and one Spirit…one Lord, one faith, one baptism, one God and Father of all, who is over all and through all and in all" (Ephesians 4:4–6).

Although Jesus designed the church for unity, even Paul witnessed a lot of false teachings, jealousy, pride, and sin as he ministered to the Gentile church. Today, there are seemingly countless examples of churches whose members disagree on a grand scale, causing their local church to fall. Paul reminds us that we choose if we will remain loyal to our local body of believers (1 Corinthians 1:10–13). We should remember that ultimately we are members of God's universal church which is based on the unity of the Trinity and the one faith of its members. God's house will never fall (Matthew 16:18).