Charles Ellicott Commentary 1 Thessalonians 4:7

"For God called us not for uncleanness, but in sanctification." — 1 Thessalonians 4:7 (ASV)

For God.—This gives the reason for stating that the Lord will take vengeance on such sins, because they are not part of the terms on which His Father called us. It should be “did not call.” These verses, 1 Thessalonians 4:7–8, sum up the little disquisition, returning to the principle announced in 1 Thessalonians 4:3.

Unto uncleanness, but unto holiness.—The preposition translated “unto” has the same force in Galatians 5:13, Called unto liberty, and Ephesians 2:10, Created unto good works. It implies not so much the definite end to which we are invited, as the terms on which the invitation will still stand; for the call is not yet accomplished (see Note on 1 Thessalonians 2:12). The second “unto” in the Greek is simply “in,” used in the same sense as in 1 Thessalonians 4:4. Paraphrase: “For God did not call us on the understanding that we might be unclean, but by the way of sanctification.”

Holiness is a mistranslation for sanctification. The process, not the quality, is meant.