Tim Challies has a long detailed look at calvinism and evangelism that is well worth reading for those who do not understand why someone who believes in sovereign grace feels the need to spread the good news of the gospel far and wide.
Here is the question Tim is answering.
“Given the tenets of total depravity (the spiritually dead are unable to choose God), unconditional election (saved through God’s sovereign choice) and irresistible grace (once God chooses you and regenerates you, you can’t NOT embrace Him)… what does a Calvinist see as the purpose of proclaiming the Gospel? Does a gospel presentation simply provide the context in which God ‘pulls the trigger’ of regeneration and faith for those He has already chosen? (cf Acts 13:48.)”
Tim notes that:
This question introduces an apparent antinomy–an appearance of contradiction between conclusions which seem equally logical, reasonable or necessary. The antinomy we face is what we perceive as tension between God’s sovereignty and human responsibility. In short, how does our responsibility to evangelize interact with God’s absolute sovereignty in the salvation of souls?
Tim then shares what christians do not have a responsibility to do in witnessing and what we do have responsibility to accomplish.
and then he gives this paragraph which is key.
To be consistent with Reformed theology we must say that if a person is one of the elect, he will come to faith and repentance. It is divinely predestined that this will happen and it is impossible for it not to happen. But God has not shared with us two vital pieces of information. He has not told us just who the elect are and how they will be brought to repentance. He has decreed that we are to share the message with everyone, in every way possible (within the bounds He sets in His Word). Charles Spurgeon once said “if all the elect had a white stripe on their backs I would quit preaching and begin lifting shirt tails” (or something to that effect). God has not put a visible mark on the elect, so we are to treat all men as if they are among the elect, and are to share the Gospel far and wide. We need to share it with a sense of urgency.
we must implore those we know to be reconciled to God and we must do so today.
Tim’s conclusion is right on the money.
Ultimately we need to understand that God has not seen fit to share with us exactly how human responsibility and Divine sovereignty interact in evangelism. While we need to always remember that God is the only one who can bring about salvation, He has decreed that we will be the instruments He uses to take the Good News to the world. And that is what we must do, all the while asking God to equip us to be worthy ambassadors for Him.
Taking another angle, perhaps God wants us to share the gospel with everyone so that no one in the “non-elect” category can say, in honesty, that “no one told me.” Their guile will be clear. In other words, so that come judgement day “every tongue will confess”. Not the right answer, just a different angle.