Jesus used the interruption to teach who His true family is. Gill says the question was asked "not through ignorance or contempt." He suggests Jesus was either displeased with the interruption or took the moment as an opportunity of "expressing his superior value to his spiritual relations." Barnes says the question was meant to "fix the attention" of the hearers and prepare them for the answer, and he adds, "There was no want of affection or respect in Jesus toward his mother, as is proved by his whole life."

The moment also follows a hard scene. Earlier, "his friends" set out "to lay hold on him," saying, "He is beside himself" (Mark 3:21). Barnes understands these friends as "his relatives," not the apostles.

Jesus answered His own question with a look and a declaration. "He looked round about on them which sat about him, and said, Behold my mother and my brethren!" (Mark 3:34). Gill says He looked around "to find out his disciples among them." Then He explained: "For whosoever shall do the will of God, the same is my brother, and my sister, and mother" (Mark 3:35). Matthew adds that He "stretched forth his hand toward his disciples" (Matthew 12:49).

The crowd around Jesus was so great that He and those with Him "could not so much as eat bread" (Mark 3:20). His family could only stand "without" and send a message in (Mark 3:31). Luke says they "could not come at him for the press" (Luke 8:19).

Mark later names four brothers of Jesus, "James, and Joses, and of Juda, and Simon," and mentions His sisters (Mark 6:3). Notice that Jesus adds "my sister" in Mark 3:35, though only His mother and brethren are said to be outside. His new family includes women and men alike.

Jesus opens His family to anyone who does the will of God. The word is "whosoever" (Mark 3:35). Barnes writes, "Dear and tender as were the ties which bound him to his mother and brethren, yet those which bound him to his disciples were more tender and sacred." Matthew Henry calls it "a great comfort to all true Christians, that they are dearer to Christ than mother, brother, or sister" as relations in the flesh.

The Gospels describe this family in three ways: those who "do the will of God" (Mark 3:35), those who do "the will of my Father which is in heaven" (Matthew 12:50), and "these which hear the word of God, and do it" (Luke 8:21). In a chapter where some said He was beside Himself and others said He had Beelzebub (Mark 3:21-22), Jesus defines belonging not by blood or by religious position, but by doing God's will.