where did Dimmesdale turn for strength?

Dimmesdale's momentary solidarity with Hester and Pearl seem to strengthen his resolve (recall his encounter with them on the scaffold).

"The moment that he did so, there came what seemed a tumultuous rush of new life, other life than his own, pouring like a torrent into his heart, and hurrying through all his veins, as if the mother and the child were communicating their vital warmth to his half-torpid system. The three formed an electric chain."