This man had been instructed in the way of the Lord; and being fervent in spirit, he spoke and taught the things about Jesus accurately, although he knew only John’s baptism. – Acts 18:25
Apollos accomplished much for the Kingdom of Christ. Some have even suggested that he might be the author of the biblical Letter to the Hebrews. Sadly, we don’t know all that he did, but may only surmise that his impact was great. Instructed in the way of the Lord and fervent in spirit, he spoke and taught about Jesus accurately. Apollos was an effective servant of His Savior. Yet, he needed something. He needed someone to teach him.
We all need teachers. In this case, Apollos had never been biblically immersed (post-conversion, trinitarian) and it fell to Aquila and Prisca to refine his understanding. Was Apollos a disciple of Christ? Absolutely. Was he useful to the Lord? Of course. It was his own role as a leader that required a correct theology and a clear testimony … and lacking either of these could have eventually made him a heretic.
Apollos was “almost right” before he met his friends, but there is nothing more dangerous in the kingdom than being “almost right.”
What makes you a Christian is whether or not you really are in accord with biblical theology and whether you know Jesus Christ as your Savior. – Walter Martin