He came to battle death. There is no greater enemy than death. Not the Scythian and Babylonian armies that the people of Zephaniah's day feared. Nor the threats of our own time. Never mind the misguided notion that floats around these days that death is a friend, something to be welcomed and sought.
Death is the curse against our sin.
It is the enemy, and Christ is the Conquerer. He conquered death by dying, and He gives us His death for our life. Never again will you fear any harm. That is reason for rejoicing. The second reason for rejoicing is God's real presence among His people.