Why is Arthur dimmsdale jealous of Hester prynne?

Aurthur Dimmsdale is the man that Hester committed adultery with. Hester is 'caught' because she becomes pregnant when her husband is away, so she has to deal with her punishment in public. She is forced to wear a scarlet letter on her chest, and is isolated from the rest of the community. Although this may not seem like a good life, Dimmsdale is jealous because he feels guilty, but can't tell anyone of his sin.

In their community, Dimmsdale is a very popular and well thought of minister. Because of this, no one would ever suspect that it was he who had an affair with Hester. During his sermons, he tries to tell the people that he too has sinned, but they don't believe him. Because of his inability to confess, he ends up having to keep his guilt to himself. This is his internal punishment.

Dimmsdale is jealous of Hester because she faced her sins and dealt with her punishment, and now can move on with her life, while he will be weighted down with guilt until he confesses.