Let me tell you may be rendered as, “I want you to know,” or “I want to make it perfectly clear.”

Paul affectionately addresses his readers as my brothers. Among Jews the word “brother” was used for the members of any given family or tribe or sect. Early Christians carried this usage over into their fellowship and addressed each other as “brothers.”

The gospel I preach could be understood either as referring to that particular message which Paul preached to the (Galatians New American Bible “The gospel I proclaimed to you”; New English Bible “the gospel you heard me preach”) or as a general reference to the message which Paul continued to proclaim (as in Good News Translation, compare Moffatt “The gospel that I preach”). The verb preach is often rendered in a form which indicates habitual action, for example, “the gospel that I customarily preach,” or “… announce.”

Is not of human origin is literally “is not according to man,” and may mean that the gospel (1) is not of human origin, (2) is not dependent on human authority, or (3) is not a human gospel. Some translations (notably New American Bible, New English Bible, along with Good News Translation) follow the first of these alternatives, while others adhere to the third (for example, Jerusalem Bible “the Good News … is not a human message,” Moffatt “is not a human affair”). The closest equivalent to is not of human origin may be “was not thought out by people,” “people did not cause it to be,” or “people did not start it.”

Quoted with permission from Arichea, Daniel C. and Nida, Eugene A. A Handbook on Paul’s Letter to the Galatians. (UBS Handbook Series). New York: UBS, 1976. For this and other handbooks for translators see here .