فَالْوَاجِبُ ضَرْبَانِ:
Translation: The obligatory category is itself of two kinds.
Quduri divides the obligatory class into two. One is attached to a definite time; the other remains owed in a person’s liability without a specific assigned day.
A predetermined date identifies the duty in the first class. In the second, the worshipper must identify which outstanding fast is being discharged.