A cause comes before the duty that results from it. If the whole prayer window had to pass before it served as the cause, the prayer would become obligatory only after that window ended.
But time is also its container: the prayer belongs inside the window, not only after it. Connecting the cause to the portion next to the start of prayer preserves both roles:
• the cause precedes the performance;
• the performance occurs inside the appointed time.
In the separate case of Qada prayer, the whole elapsed window is its cause. The prayer was not performed within its appointed container. Letting its time pass and leaving it for Qada carries the severe warning of sin; the Qada label does not make neglecting its time acceptable.
- Why Not Treat the Whole Window as the Cause?