Just as babies drink milk and mature people eat solid food, new followers of Jesus require spiritual milk and need to be fed; whereas established followers should be able to feed themselves, that is, grow spiritually.
When believers can spiritually feed themselves, they are spiritually mature.
This concept is discussed in 1 Corinthians 3:2 and Hebrews 5:12.
Key verse about spiritual maturity: “You, therefore, will be perfect [growing into spiritual maturity both in mind and character, actively integrating godly values into your daily life], as your heavenly Father is perfect” (Matthew 5:48, AMP).
A lifelong student of the Bible, Peter DeHaan, PhD, wrote the 1,000-page website ABibleADay.com to encourage people to explore the Bible. His main blog and many books urge Christians to push past the status quo and reconsider how they practice their faith in every area of their lives.