Christian maturity is rooted in the Word of God. This is underscored in Scripture over and over again, for example 2 Peter 3:17-18, “17Therefore, dear friends, since you already know this, be on your guard so that you may not be carried away by the error of lawless men and fall from your secure position. 18But grow in the grace and knowledge of our Lord and Savior Jesus Christ. To him be glory both now and forever! Amen.” Jesus Himself said, John 8:31-32 …“If you abide in My word, you are My disciples indeed. 32And you shall know the truth, and the truth shall make you free.”
This is why Christian Maturity and Christian Unity go together.
When we are “grownups” we take the Bible seriously, making the effort to learn it and understand it. As Christians we also believe it. The closer we all come to Biblical truth, the closer we come to one another. That is true unity. So Paul admonished the Corinthians (1 Corinthians 1:10) “10Now I plead with you, brethren, by the name of our Lord Jesus Christ, that you all speak the same thing, and that there be no divisions among you, but that you be perfectly joined together in the same mind and in the same judgment.”
Whose mind and judgment are we to join in? God’s, as He has revealed it in His word!
This calls for virtues and skills that are not taught much any more: Humility and gentleness, as Ephesians 4 stresses. But it also requires diligence and effort in learning to read and understand language in general, and the Bible in particular. It requires the use of logic as a tool subservient to the word of God. Such effort and instruction are rare, but so needed in the church if we are not to be like infants swept away by our own feelings and tantrums about what WE want to hear and to believe.