The story ends upon the 5th year of the "apprenticeship," and so Malamud never states that Sobel marries Miriam. We must deduce that Feld will change his mind in the end and let Sobel marry his daughter.
Feld had been interested in only a material future for his daughter, and he had vested his hopes in Max, whom he thought the more socio-economically successful. But Miriam told her father that Max had no soul, and so a spiritual relationship never materialized between her and Max.
Instead, Sobel proved the better match for his daughter, as he has the work ethic and the spiritual values that make for a lifelong mate. Plus, his patient waiting is testament to the love that will withstand time. Feld realizes this by the stories end, and we must assume that he will let his daughter marry him, even before two more years of servitude.
Another way to look at it, which is supported by the text, is that Feld realizes his dream of a better future for Miriam than her mother had is ruined and dead and that, whether it is what he yearns for or not, they will marry. Feld sheds his fear with this realization of his crushed dream and, since he no longer can fear what might happen (because it has already happened), he gives Sobel his blessing and walks away with a stronger stride.