What does 1 Peter 1:23 mean?

In the previous verse, Peter charged his readers to love each other deeply or earnestly from pure hearts. He connects that command to the reminder that, as Christians, we have been born again. It's an odd thought, when first read. When Jesus said to Nicodemus in John 3 that nobody can see God's kingdom unless they are born again, Nicodemus recognized the figure of speech. He saw that this was biologically impossible. Jesus made it clear that He was referring to a spiritual birth.

Being born physically does not make us alive spiritually. In fact, Paul wrote that we all start out spiritually dead in our sins (Ephesians 2:1). God is the one who makes us alive when we come to Him through faith in Christ (Ephesians 2:5–9). Peter wrote at the beginning of this chapter that God had caused his believing readers to be born again. So, as Christians who have been born again, we now have the ability to love each other with spiritually alive hearts. We can do this with all our might and complete sincerity.

This spiritual birth leads to a life that will never end. Physical birth results from a seed that dies eventually. But the new birth springs from an undying seed, through God's undying word. What is this "word of God"? In verse 25, Peter will tell us it is the good news that has been preached to us. We sometimes call it the gospel. It is the message from God that He will forgive our sins and make us spiritually alive forever in Christ.