As the novel progresses, Dimmesdale becomes more visibly weak. In chapter nine, the townspeople become so concerned about his illness that they suggest Roger Chillingworth, who the believe to be a doctor, move in with him. The town thinks his sickness is due to his hard work, long hours, and reading by lamp light.
By those best acquainted with his habits, the paleness of the young minister's cheek was accounted for by his too earnest devotion to study, his scrupulous fulfillment of parochial duty, and, more than all, to the fasts and vigils of which he made a frequent practice, in order to keep the grossness of this earthly state from clogging and obscuring his spiritual lamp. Some declared, that, if Mr. Dimmesdale were really going to die, it was cause enough, that the world was not worthy to be any longer trodden by his feet.
When the town suggests the doctor move in with their favorite minister, he initially says no. He knows the cause of is illness is nothing medicine can fix; his illness is because he cannot confess his sins with Hester and therefore can have no absolution. Because of this, the gesture he begins is placing his hand over his hear.
But how could the young minister say so, when, with every successive Sabbath, his cheek was paler and thinner, and his voice more tremulous than before,—when it had now become a constant habit, rather than a casual gesture, to press his hand over his heart