Jesus explained why their claim that he was expelling evil spirits by Satan’s power was ridiculous, and that such a claim was an unforgivable sin.

Mark 3:20-30

20 Jesus along with his disciples went to the house where he was staying in Capernaum. Again a crowd gathered where he was. There were many people crowding around him, so that he and his disciples had no time when they could eat or when they could do anything else. 21 After his relatives heard about this, they went to take him home with them because ◄some people/they► were saying that he was insane.

22 Around that time some men who taught the Jewish laws came down from Jerusalem city. They heard that Jesus was expelling demons. So they were telling people, “Beelzebub, who rules the evil spirits, controls him. He is the one who enables this man to expel evil spirits from people!” 23 Jesus summoned those men. Then he spoke to them in parables to enable them to realize that Satan would not oppose his own evil spirits. He also wanted them to realize that by expelling evil spirits, he was demonstrating that he was much more powerful than Satan. So he said, “◄It is ridiculous to suggest that Satan would expel his own evil spirits!/Why would Satan expel his own evil spirits?► [RHQ] 24 If people who live in the same country are fighting one another, they will cease to be a single group under one ruler. 25 And if people who live in the same house fight each other, they will certainly not remain as one family. 26 Similarly, if Satan and his evil spirits were fighting one another, instead of remaining strong, he would become powerless. 27 Contrary to what you say about me, someone can enter the house of a strong man like Satan and carry off his possessions only if he first ties up the strong man. Then and only then will he be able to steal the things in that man’s house.” 28 Jesus also said, “Consider this carefully! People may sin in many ways and they may speak evilly about God, but if they then are sorry and ask God to forgive them, God will forgive them for doing that. 29 But if anyone speaks evil words about what the Holy Spirit does, God will never forgive that. That person’s guilt will remain with him forever.”

30 Jesus told them that because they refused to admit that the Holy Spirit was helping him to expel demons. Instead, they were saying, “An evil spirit is controlling him!”