Isn’t it presumptuous for Christians to say they know for sure they are going to heaven?

Maybe something will happen before they die which would prevent them from going to heaven. That is what many non – Christians say about us going to heaven. But as believers in our Lord Jesus Christ, we have the assurance of eternity in heaven.

I write these things to you who believe in the name of the Son of God so that you may know that you have eternal life.

1 John 5:13

Read that verse again. Christians can know and trust in the promise God Himself gives through His Word.