De or het vesperviering?

The correct Dutch article is:

de vesperviering

Rule Words ending in -ing: almost always de. See the rule

How to use vesperviering

the vespervieringde vesperviering
this vespervieringdeze vesperviering
that vespervieringdie vesperviering
our vespervieringonze vesperviering
your vespervieringjouw vesperviering
every vespervieringelke vesperviering
which vesperviering?welke vesperviering?
a big vesperviering / the big vespervieringeen grote vesperviering, de grote vesperviering