How do we know the need for spiritual life is true?

Throughout John’s Gospel, particularly in John 3, Jesus teaches Nicodemus that being born again is essential for entering the Kingdom of God. Paul echoes this necessity in Philippians 3:3, where he highlights that true worship and identity as God's people come from being spiritually alive rather than relying on the flesh. The emphasis on spiritual rebirth underscores a foundational doctrine in Reformed theology, asserting that without divine regeneration, one cannot truly know or worship God.