[T]he sheer joyous enthusiasm of the early evangelists enhanced their absolute claims for Jesus Christ. If he really was the only way to God, if there was salvation in no other, then it is not surprising that they should commend him with such enthusiasm to others. Jesus had promised his joy as a permanent possession of his Church, a joy which no man could take from them. And they demonstrated that this was so. They might be thrown into prison for their views: but they were still singing hymns to God at midnight! It was from prison that Paul wrote Philippians, that epistle of joy and confidence. Conversion and joy are closely related in the Acts of the Apostles, and it remained a characteristic thing about the early Christians which attracted others into their company. Their new faith did not make them miserable. Often outward circumstances were unpleasant enough, but that could not rob them of the joy which was their Christian birthright. The Thessalonians received the word in much affliction . . . but equally, in joy inspired by the Holy Spirit. The disciples had an infectious joy that they were allowed to suffer for their Master’s sake. They rejoiced in the hope of sharing a future with God; they rejoiced in the sufferings which came to them along the Christian path; they rejoiced in God himself, and the companionship with him that nothing could deprive them of.

Michael Green, Evangelism in the Early Church, 185-186.