Albert Barnes Commentary Acts 18:27

"And when he was minded to pass over into Achaia, the brethren encouraged him, and wrote to the disciples to receive him: and when he was come, he helped them much that had believed through grace;" — Acts 18:27 (ASV)

Into Achaia. (See Barnes on Acts 18:12).

The brethren wrote. The brethren at Ephesus. Why he went, the historian does not inform us. But he had heard of the success of Paul there, of the church which he had established, and of the opposition of the Jews. 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.

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 sprang up in the church.

But in all this, he retained the confidence and love of Paul (1 Corinthians 1; 1 Corinthians 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 goodwill 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 refer either 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 favour of God. Either interpretation makes good sense. Our translation has adopted that which is most natural and obvious.