"Today, if you hear his voice, do not harden your hearts as in the rebellion...As in my anger I swore, 'They shall not enter my rest.'"
The author of Hebrews repeats this scripture (or a section of it) from Psalm 95 multiple times. His concern is that the people of God, once enlightened by hearing the good news, should not fall back into disobedience and thus miss out on the chance to enter God's promised rest. He does this by drawing a comparison between the Church of Jesus Christ and the Israelites in the wilderness. Both groups have received deliverance and the promise of rest. The Israelites, however, fell into disobedience and rebellion. They thus lost their opportunity to enter into God's rest.
Are disobedient, rebellious Christians liable to the same fate? Hebrews 4 would seem to indicate yes.