What does Revelation 2:21 mean?

In a remarkable display of grace, Jesus had given a woman identified as Jezebel time to repent, despite her leading Christians into immorality (Revelation 2:20). However, she rejected Jesus' kindness. Her heart was hardened and set on pursuing sexual sin. She was like the people of Sodom, who did not repent of their sexual immorality despite the presence of righteous Lot in their city (2 Peter 2:7–8). It is clear from this verse that legitimate repentance includes a forsaking of sin.

God's grace is His unmerited favor. Even the most hardened sinner can be forgiven if he responds appropriately to God's grace and turns from his sin. The apostle Paul called himself the foremost of sinners (1 Timothy 1:15) and reflected on the amazing grace that saved him. He wrote in 1 Timothy 1:14 and 16: "the grace of our Lord overflowed for me…I received mercy for this reason, that in me, as the foremost, Jesus Christ might display His perfect patience as an example to those who were to believe in him for eternal life."

Unbelievers must not presume upon God's patience, however. Thinking that they can plan to repent "someday," perhaps when they lie on their deathbed, may bring an alarming end to their presumption. Proverbs 27:1 commands, "Do not boast about tomorrow, for you do not know what a day may bring." Also Proverbs 29:1 posts the warning, "He who is often reproved, yet stiffens his neck, will suddenly be broken beyond healing."