God is the one who issued the call. Ye were called brings out the fact that God took the initiative in bringing men to salvation. God's purpose in calling to salvation was not for uncleanness but unto holiness. But marks the strong contrast between these two conditions. Uncleanness is a general term for moral impurity, which expressed itself in many ways.
Holiness refers to the progressive holiness of growing in the Christian life.
The ones who are called must follow through in their call to progressive holiness. A caution against living impure lives is given in verses 6b and 8. The Lord is characterized as the avenger or one who punishes or extracts legal justice from a wrongdoer. He satisfies justice by inflicting due punishment upon the wrong doer. In all such refers to the different forms of sexual impurity.