Witnesses to Grace, Heralds of Damnation

"And indeed, does it lie within us [preachers] to promise men life everlasting or to denouce against them the vengeance of God? And yet we do it nevertheless, but we go no further than the Word of God, as it is put into our mouths. We have His testimony that we are his witness and heralds. By His "witnessess" I mean we assure the faithful of the grace and salvation promised to them and as His "heralds" we pronounce and publish His sentence against all the unbelieving and against all rebels." (John Calvin, Sermon on Deuteronomy 28:1-2)