What does Hebrews 3:8 mean?

This verse continues a quotation of Psalm 95. There, God's people are warned not to disobey out of fear or a lack of belief. In Numbers chapters 13 and 14, Israel does just that. After being miraculously rescued from Egypt, Israel sent spies into Canaan, which God had given them to capture. Of the twelve spies sent, only two expressed faith in God. The other ten, along with most of Israel, balked at the idea of fighting the "giants" of Canaan. As a result, God put the nation through a time of discipline and testing. Only a tiny remnant of those alive at that moment of failure would survive to enter the Promised Land.

The Greek of the New Testament uses the terms parapikrasmō and peirasmou when quoting Psalm 95, from the Septuagint translation of the Old Testament. These words mean "provocation" and "trial," respectively. The ESV translates these as "rebellion" and "testing." Both in the Greek and the Hebrew these are references to events and to places. The original Hebrew uses the place-names Meribah and Massah, which literally mean "strife" and "temptation." Meribah and Massah (or Massah and Meribah) was the name given to the place at Kadesh where Israel complained against God and saw water come miraculously from a rock (Numbers 20:2–13). This was the incident which cost Moses his own entry into the Promised Land.