# no man

"no one" or "no person" 

# transgress and wrong his brother

Possible meanings: 1) The words "transgress" and "wrong" are a doublet that emphasizes the idea of harming the brother. Alternate translation:  "do very wrong things to his brother”and  2) The word "transgress" refers to sinning against God, and "wrong his brother" refers to harming the brother. Alternate translation: "do what God had forbidden and wrong his brother”

# the Lord is an avenger

"the Lord will punish the one who transgressed and will defend the one who was wronged" 

# forewarned you and testified

"told you beforehand and strongly warned against"