Psalm 95:7-11 in Hebrews 3 & 4
¡7 (NIV) É Today, if you hear his voice, 8 do not harden your hearts as you did at Meribah, as you did that day at Massah in the desert, 9 where your fathers tested and tried me, though they had seen what I did. 10 For forty years I was angry with that generation; I said, "They are a people whose hearts go astray, and they have not known my ways." 11 So I declared on oath in my anger, "They shall never enter my rest."
¡The author of Hebrews is warning his readers about the danger of apostasy.