Signs of maturity in Christians
The ability to display Godly love is a key sign of a mature Christian. God has called us to imitate him. The apostle Paul stated to the Ephesian church that they should walk or live in love just as Christ practiced when he walked the earth (Ephesians 5:1 - 2).
Believers are to develope the character to love on a spiritual plane. The more of God's spirit in us and the more we wield to its influence, the better our ability to love as God does will become. Paul wrote that God pours out the love he has into us through the effective working of his spirit (Romans 5:5).
Signs of immature Christians
There are many people who think they have reached maturity in the faith but in reality the act more like little spiritual children. What reasons do people use to justify their view that they (or even someone else) are more grown up and 'spiritual' than others? Some of these reasons include being a church member for years, having intimate knowledge of church doctrines, going to services every week, being old or able to effectively put others down. Other reasons include spending time with church leaders, being financially well-off, giving significant sums of money to the church, knowing quite a bit about Scripture or dressing well to church.
Jesus' new command
As I have loved you, so you must love one another. 35 If you have love for one another, then everyone will know that you are my disciples. (John 13:34 - 35).
How we treat fellow Christians in public is a sign not only that we are converted but that we are also mature in the faith. And, just like faith, love without works is spiritually dead. True love must be demonstrated on a consistent basis by how we live our lives. Needless to say, hate has no place in the life of a Christian. To the degree in which we hate is the degree to which we are still immature.
The definition of spiritual maturity
Paul teaches us what maturity on a spiritual level is and is not. In 1Corinthians 13 he states the real love of God is patient, kind, does not envy or brag, or is full of vanity. It does not behave rudely, nor is selfish, nor is it easily provoked. Godly love never rejoices in sin but always does so regarding the truth. It bears all things and "believes all things, hopes all things, endures all things." (see 1Corinthians 13:4 - 7)
Since the love of God never fails, his love within us projected to others ought to not fail either (verse 8).
The person who has reached a measure of spiritual maturity is not preoccupied with self. Those who are mature have come to a level where no longer interest themselves in the sins of others (1Corinthians 13:5). They no longer keep a record, as Paul put it, of the sins committed by others.
A mature spiritual believer rejoices in the truth of God. They pursue truth and let it take them to wherever it leads.
Mature believers have no desire to indulge in evil nor do they try to take advantage of others when they indulge in it. They are always working to remove the spiritual darkness that engulfs the world and to protect those who are vulnerable to its dangers. Those who are mature Christians dedicate time to pray for others (1Thessalonians 5:17).
Love enables us to persevere and have hope in what God can do. Those who are mature in the faith are friends to others not only in the good times but also the bad.
The power to reach it
Having spiritual maturity involves be sensitive to the power and leadership of God's spirit. It offers us the ability to possess the same kind of AGAPE love as God. As we grow in grace and knowledge, and obey God with our whole heart, his Spirit grows as well (Acts 5:32). The apostle Paul prayed that the believers in Ephesus be filled with Christ and comprehend the multiple dimensions of his divine love (Ephesians 3:16-19).
God's Spirit in us makes us His chosen people (Acts 1:8). It gives us the ability to overcome and be victorious over our self-destructive human nature. The more of God's Spirit we have, the faster we will become the spiritually mature Christians God desires for all his children.