We Christians are called to be child-like, not childish (1 Cor 14:20). Being childish means being "tossed here and there, carried about by every wind of doctrine that originates in human trickery and skill in proposing error" (Eph 4:14). It means being manipulated and enslaved.
The way to freedom from childishness is to profess the truth in love (Eph 4:15). The truth will set us free (Jn 8:32) and have us "grow to the full maturity of Christ the Head" (Eph 4:15).
We grow up and grow out of childishness by obeying apostles, prophets, evangelists, and pastor-teachers who will equip us for the work of service to build up the body of Christ (Eph 4:11-12). Thus, the truth that sets us free from childishness is not just general spiritual information; it is the truth that prepares us for full-time service to Christ and His body. This is the call of all baptized people.
Furthermore, the truth that frees and equips us for service is based on the Bible. "All Scripture is inspired of God and is useful for teaching — for reproof, correction, and training in holiness so that the man of God may be fully competent and equipped for every good work" (2 Tm 3:16-17).
Therefore, study and know God's Word in the Scriptures to prepare for God's service, or else live the enslaved, confused life of a child. Grow up or be manipulated. It's the Bible and God's service, or confusion and darkness. "Let us, then, be children no longer" (Eph 4:14).