Into Achaia - See the notes on Acts 18:12.
The brethren wrote - The brethren at Ephesus. Why he was disposed to go into Achaia the historian does not inform us. But he had heard of the success of Paul there; of the church which he had established; of the opposition of the Jews; and it was doubtless with a desire to establish that church, and with a wish to convince his unbelieving countrymen that their views of the Messiah were erroneous, and that Jesus of Nazareth corresponded with the predictions of the prophets, that he went there. Many of the Greeks at Corinth were greatly captivated with his winning eloquence 1 Corinthians 1:12; 1 Corinthians 3:4-5, and his going there was the occasion of some unhappy divisions that sprung up in the church. But in all this he retained the confidence and love of Paul, 1 Corinthians 1:3. It was thus shown that Paul was superior to envy, and that great success by one minister need not excite the envy, or alienate the confidence and good will of another.
Helped them much - Strengthened them, and aided them in their controversies with the unbelieving Jews.
Which had believed through grace - The words “through grace” may either refer to Apollos, or to the Christians who had believed. If to him, it means that he was enabled by grace to strengthen the brethren there; if to them, it means that they had been led to believe by the grace or favor of God. Either interpretation makes good sense. Our translation has adopted what is most natural and obvious.