What does Hebrews 3:9 mean?

This continues a quotation from Psalm 95. The author of Hebrews is pointing out the danger facing a Christian who does not "hold fast" to their faith when persecuted. The illustration from Psalm 95 refers to the failure of Israel in the wilderness just before they reached the Promised Land. Verse 8 mentioned "rebellion" and "testing," which are both events and the names given to certain places. In the Hebrew of Psalm 95, these are Meribah and Massah, which mean "strife" and "temptation." This was the place Israel complained against God.

This verse more specifically mentions Israel's forty years of wandering. This was an act of discipline given by God. Rather than trusting Him—"holding fast"—they responded in doubt and fear when asked to move into Canaan (Numbers 13—14). So God forced them to wander aimlessly in the wilderness for decades. The application which the author of Hebrews intends comes most clearly in Hebrews 3:12–19. Christians who lose faith in the face of persecution can expect to lose fellowship and reward. They don't lose salvation (just as Israel was not sent back to Egypt), but they will suffer a loss of their spiritual inheritance.