What does Hebrews 3:11 mean?

The author of Hebrews is using a quotation of Psalm 95 to illustrate an important point. Earlier verses explained that Jesus is a greater example than Moses, and so we should seek to follow Christ, even in times of hardship. Psalm 95 is a warning to Israel not to lose faith in God, as they did after leaving Egypt. Christians, then, are called on to "hold fast" to their faith, even under persecution, so they don't lose their fellowship and inheritance with God.

The reference to "rest" here needs to be carefully understood. This part of Hebrews uses several meanings of "rest." This verse is a reference to Israel's victory in Canaan, as intended by God (Deuteronomy 12:9). The rebellious, faithless generation of Israel in the desert was barred from obtaining this victory. The Promised Land, however, is not meant to be a metaphor for salvation. Israel still had temptations, battles, and strife in Canaan. So, this is not a reference to a loss of salvation, for a Christian. This is further supported by the fact that Hebrews 4:9 will appeal to an eternal, ultimate "rest" of heaven, separate from what is mentioned here.