“And when he was disposed to pass into Achaia, the brethren wrote, exhorting the disciples to receive him: who, when he was come, helped them much which had believed through grace:”
King James Version (KJV)
18:27 Who greatly helped through grace - It is through grace only that any gift of any one is profitable to another. Them that had believed - Apollos did not plant, but water. This was the peculiar gift which he had received. And he was better able to convince the Jews, than to convert the heathens.
Ac 18:27 When he was disposed to pass into Achaia. Greece, the province of which Corinth was the Roman capital. The brethren wrote. This is the first instance of church letters. This was written to show the brethren at Corinth that the bearer was worthy of their confidence. They no doubt testified to his soundness in the faith and Christian character. Paul alludes to such letters in 2Co 3:1. Helped them much. The believers at Corinth. Apollos was God's instrument to help them (see 1Co 3:5,6). Through grace. Through the Divine favor.