The verse serves as a warning against hardening one's heart towards God. It reminds us of the Israelite's rebellion and disobedience when they were in the wilderness, and how they hardened their hearts towards God. Our lives should not repeat the same mistakes and we need to remain open to God's guidance and direction. Furthermore, it implies that it is never too late to seek forgiveness from God.
Often, the disobedience of the first generation of Jews has been referred to as "unbelief" and "rebellion". By putting God to the test, it gives the world a reminder of the seriousness of our actions. As a consequence of the Israelite's actions, they were deprived of their promised rest and spent 40 years wandering in the wilderness. Our failure to trust in God's guidance and provision serves as a warning to us not to repeat the mistake.
It is easy to criticize Israel for its lack of faith and rebellion, but how often do we fail to trust God's Word? How often do we complain about the circumstances of our lives or the things that are going on in them? It would be wiser to learn from Israel's mistakes and ensure that we do not harden our hearts or seek to resist God instead of looking on in reproach.

Dear Heavenly Father, I confess that I have at times hardened my heart towards You, just as the Israelite did at Meribah and Massah in the wilderness. I ask for Your forgiveness and grace. I pray that You help me to not repeat their mistakes and to remain open to Your guidance and direction in my life. I ask that You help me to not test You or rebel against You but to trust in Your provision and Your promises. I want to enter into Your rest, so please help me to not harden my heart but to keep it soft and pliable in Your hands.
In Jesus's name I pray. Amen.