In these passages is the account of Paul and Barnabas returning to cities where they had proclaimed the Word of God to see how the brethren were doing. They were intending to strengthen the Faith of new believers. That is one function or purpose of the Church. The Church provides a means for believers to share their Faith and strengthen one another.
The path to Salvation is a difficult path, and believers may become discouraged along the way. Other believers are needed to encourage them to remain on this difficult path. As their Faith grows, they can encourage others.
One’s Faith is not static. It must increase. With each trial it will increase, as one learns to rely on God for guidance and help.
The Bible says, “Without Faith it is impossible to please God.” The Bible also says, “We are saved by Grace through Faith.” This saving Faith is evidenced by good works that produce good fruit in our lives.