Whether we are sharing the Gospel, explaining the biblical worldview or defending the faith, we can be confident in what this verse promises.
Those who are Christ’s sheep—whom God has chosen beforehand to be saved—will, in God’s perfect timing, hear the Gospel and believe it.
As limited, very finite human beings, we don’t know whom God has chosen. So we teach the good news to everyone we can. We won’t always see the end result of repentance and faith, but we can trust beyond the shadow of a doubt that God is working out his plan. The Good Shepherd will gather all his sheep.