He had been instructed in the way of the Lord; and being fervent in the spirit, he spoke and taught accurately the things concerning Jesus, though he knew only the baptism of John.

Acts of the Apostles 18:22-28

IN THOSE DAYS, when Paul had landed at Caesarea, he went up and
greeted the church, and then went down to Antioch. After spending some
time there he departed and went from place to place through the region
of Galatia and Phrygia, strengthening all the disciples. Now a Jew
named Apollos, a native of Alexandria, came to Ephesos. He was an
eloquent man, well versed in the scriptures. He had been instructed in the
way of the Lord; and being fervent in the spirit, he spoke and taught
accurately the things concerning Jesus, though he knew only the baptism of
John. He began to speak boldly in the synagogue; but when Priscilla and
Aquila heard him, they took him and expounded to him the way of God more
accurately. And when he wished to cross to Achaia, the brethren encouraged
him, and wrote to the disciples to receive him. When he arrived, he
greatly helped those who through grace had believed, for he powerfully
confuted the Jews in public, showing by the scriptures that the Christ was
Jesus.