How does rejecting the gospel each time affect a person's ability to believe later?
Each rejection of the gospel hardens the person further. Saying no makes the next no easier, while recognition of God’s mercy shrinks and rebellion grows. Repeated refusals build barriers of resistance, so later belief becomes much harder; for one still rebelling against grace into old age, it is almost impossible to break through.
Les explains this from Pharaoh’s example. When God brought Pharaoh to a tough decision, Pharaoh chose his own direction. After each plague Moses asked whether he was ready to let the Jews go; Pharaoh could have said, 'Let them go,' but instead said, 'I’ll not let them go.' Les sees the same human nature today: when people are brought to a place of deciding for or against God and say no, the next time it is easier to say no. Their whole concept of rebellion grows, and their recognition of God’s mercy gets smaller. So when people grow old and remain rebels against the grace of God, it is hard to break through—almost impossible because they are so hardened. Les has talked to a few and says you just cannot get through to them. Sometimes you can, but usually it is so hard because every time they were confronted with believing the gospel and rejected it, it becomes that much harder at some future time to break down those barriers of resistance. And so it was with Pharaoh.