What does Hebrews 3:7 mean?

This chapter points out that Jesus is a greater example than Moses. As a result, the Jewish Christians who read this letter should see Christ as the ultimate example, and "hold fast" to faith in Him despite hard times. Here, the author of Hebrews introduces an example from Israel's history to explain what happens when a saved believer fails to "hold fast" in their trust for God. This is given in a quotation from Psalm 95:7–11, starting here and running through verse 11.

Psalm 95 depicts the dangers of a believer "hardening their heart" against God, specifically by being fearful or disobedient. Israel did just that in the wilderness, and as a result, God disciplined the nation with forty years of wandering.

The reference to the Holy Spirit is not the major point of this passage, but it is important. The writer of Hebrews, clearly, sees the Scriptures of the Old Testament as inspired by the Holy Spirit. These texts are not simply being quoted because they are familiar to the letter's readers. They are being quoted as the very words of God.

The term "today" is meant to imply urgency. This is not a trivial idea being discussed: this is immediate.