Acts 8:37

And Philip said. If thou believest with all thine hearty thou mayest. And he answered and said, I believe that Jesus Christ is the Son of God The whole of this verse is omitted in the oldest MSS. It probably found its way into the text of those MSS. where it does exist from the margin. Such a margin would be formulated by those who, when the Church had become more extended, and formal professions of faith were the rule before baptism, felt that there was a want of completeness in the narrative unless some such confession were supposed to have been made. Thus the margin became a kind of exposition, and in the end found acceptance in the text.