Albert Barnes on 1 Thessalonians 4:7

For God hath not called us unto uncleanness. When he called us to be his followers, it was not that we should lead lives of impurity, but of holiness. We should, therefore, fulfil the purposes for which we were called into his kingdom. The word uncleanness, (ακαθαρσια) means, properly, impurity, filth; and then, in a moral sense, pollution, lewdness, as opposed to chastity, Rom 1:24, 6:19, 2Cor 12:21, Gal 5:19; Eph 4:19, 5:3, Col 3:5.

(b) "unto holiness" Lev 11:44, Heb 12:14, 1Pet 1:14-16