In Mark 6:1-3 we see Jesus entering his hometown of Nazareth (6:1). He is traveling with his disciples and teaching in the synagogue on the Sabbath (6:2). The people in his hometown are astonished at his teachings and doubt his authority, wisdom, and works (6:2). They probably recognized that the authorities of his teachings (and the teachings themselves) were taught with the authority of God. Also, his wisdom and works were not those of a mere human. Immediately, they start questioning the authenticity of these things by stating the obvious: he is a carpenter, the son of Mary and brother of James and Joses and Judas and Simon (6:3). These people of Nazareth watched Jesus grow up! They knew his parents, his brothers, and his sisters. He cannot be God, they thought; he is a man! They took offense at him (6:3) because he has proclaimed things that set him higher than them, namely, his divinity.
The fact that the people could not recognize the divinity of Jesus makes a greater point for his humanity. He was perceived b other people to be human. This seems to be the most important part of the passage; Jesus’ humanity was obvious! This passage boosts a defense against the Christological heresies such as Docetism and Appolinarianism. Docetism denies the Jesus was truly human because the flesh was evil. Appolinarianism also believes that Jesus’ humanity was swallowed up in his deity, creating a new nature. Again, this passage is strong evidence against such a view in that those who grew up with Jesus recognized him as fully man.
The practical importance for the humanity of Christ as expressed in Mark 6:1-3 is that Jesus lived a human life. Like all of us, Jesus was born into a family with parents and siblings. He had to go through the same daily routines such as work (in his case, as a carpenter). He also experienced denial by people in his hometown. As followers of Jesus, we can be confident that we are following someone who knows what it feels like to be in a family, working in a job, and being rejected by people who ought to be supportive. The humanity of Jesus gives us hope for our lives.