51 DJ

Chapter 22
"There was no feebleness of step as at other times; his frame was not bent, nor did his hand rest ominously upon his heart. Yet, if the clergyman were rightly viewed, his strength seemed not of the body. It might be spiritual and imparted to him by angelical ministrations. [...] Nevertheless, so abstracted was his look, it might be questioned whether Mr. Dimmesdale even heard the music."

Of course, "it might be" means it is. A.D. of course is relieved: first of all, he finally decided not to feel guilty in secret, but declare it. This means that his pain has not reason to be, and the symbol of his pain is the gesture he made wih the hand. Besides, I do remember that Pearl asked one if, after they held their hands at mid-day, the  hand on his heart would have been yet. Well, we see her that now that D. decided to do this, his pain disappeared.
Angelical strenght?  of course we're talking about Pearl! (and Hester). She has more than once been compared to the angelical world because of her "skills", and here we see the effects of her power. Pearl is an angel sent to help A. and H., and we see here that she actually saves her father giving him the strenght.