The last phrase, "who had believed through grace," parallels the thought in Acts 13:48: "And as many as had been appointed to eternal life believed." It reinforces that our belief is the consequence, not the cause, of God calling us, even as His predestinating us to eternal life causes us to believe. This also clarifies that God appoints only a limited number to eternal life in this age, and by grace, God's gift, He imparts to them the faith to submit to Him. Some believed the preaching of Paul and some did not. Those whom God gave faith by grace were greatly helped by Apollos, to whom God had also given faith.