Suppose Hajj is already obligatory on a person, but they expressly intend a voluntary Hajj. The result in this example is voluntary Hajj: the obligatory Hajj is not discharged.
Why does this differ from general intention? Hajj time also has the container-like aspect. An explicit voluntary intention can therefore be valid; the time does not force every Hajj intention to become obligatory Hajj.
The accompanying analogy is a voluntary prayer performed before the obligatory prayer within a prayer time. It illustrates how time may contain a voluntary act without that act becoming the obligation.
General intention may fulfill the obligation here; explicit voluntary intention does not.
- An Explicit Voluntary-Hajj Intention