'Mature' in the Bible

Yet we do speak wisdom among those spiritually mature [believers who have teachable hearts and a greater understanding]; but [it is a higher] wisdom not [the wisdom] of this present age nor of the rulers and leaders of this age, who are passing away;

Brothers and sisters, do not be children [immature, childlike] in your thinking; be infants in [matters of] evil [completely innocent and inexperienced], but in your minds be mature [adults].

until we all reach oneness in the faith and in the knowledge of the Son of God, [growing spiritually] to become a mature believer, reaching to the measure of the fullness of Christ [manifesting His spiritual completeness and exercising our spiritual gifts in unity].

All of us who are mature [pursuing spiritual perfection] should have this attitude. And if in any respect you have a different attitude, that too God will make clear to you.

We proclaim Him, warning and instructing everyone in all wisdom [that is, with comprehensive insight into the word and purposes of God], so that we may present every person complete in Christ [mature, fully trained, and perfect in Him—the Anointed].

Epaphras, who is one of you and a bond-servant of Christ Jesus, sends you greetings. [He is] always striving for you in his prayers, praying with genuine concern, [pleading] that you may [as people of character and courage] stand firm, [spiritually mature] and fully assured in all the will of God.