That no man go beyond - ὑπερβαίνειν huperbainein. This word means, “to make to go over,” as, e. g., a wall or mountain; then, to overpass, to wit, certain limits, to transgress; and then to go too far, i. e., to go beyond right - hence to cheat or defraud. It is not used elsewhere in the New Testament. The idea of overreaching is that which is implied in its use here.
And defraud - πλεονεκτεῖν pleonektein Margin, “oppress,” or “overreach.” This word properly means, to have more than another; then to have an advantage; and then to take advantage of any one, to circumvent, defraud, cheat. It is rendered “got an advantage,” 2 Corinthians 2:11; “defraud,” 2 Corinthians 7:2; 1 Thessalonians 4:6; “make a gain,” 2 Corinthians 12:17-18. Compare for the use of the adjective, 1 Corinthians 5:10-11; 1 Corinthians 6:10; Ephesians 5:5; and the noun, Mark 7:22; Luke 12:15; Romans 1:29; 2 Corinthians 9:5; Ephesians 5:3; Colossians 3:5; 1 Thessalonians 2:5; 2 Peter 2:3, 2 Peter 2:14. It is the word commonly used to denote covetousness. Taking advantage of, is the idea which it conveys here.
In any matter - Margin, “or the.” According to the reading in the margin, this would refer to the particular matter under discussion 1 Thessalonians 4:3-5, to wit, concupiscence. and the meaning then would be, that no one should be guilty of illicit intercourse with the wife of another. Many expositors - as Hammond Whitby, Macknight, Rosenmuller, and others, suppose that this is a prohibition of adultery, and there can be no doubt that it does include this. But there is no reason why it should be confined to it. The Greek is so general that it may prohibit all kinds of fraud, overreaching, or covetousness, and may refer to any attempt to deprive another of his rights, whether it be the right which he has in his property, or his rights as a husband, or his rights in any other respect. It is a general command not to defraud; in no way to take advantage of another; in no way to deprive him of his rights.
Because that the Lord is the avenger of all such - Of all such as are guilty of fraud; that is, he will punish them; compare Romans 12:19 note; Ephesians 6:9 note.
As we also have forewarned - Doubtless when he was with them.