We know this how? The majority of his life is not described in scripture. His birth is reported, a very brief sketch of his youth is described in scripture, and then he goes off radar until he is described as being about thirty years old.
How do we arrive at the conclusion that he was a manual laborer?
No hostility here, just want to know.
Mar 6:3 Is not this the carpenter, the son of Mary, the brother of James, and Joses, and of Juda, and Simon? and are not his sisters here with us? And they were offended at him.