Ulangan 23:9

Purity in Personal Hygiene

23:9 When you go out as an army against your enemies, guard yourselves against anything impure. ¹ 

Ulangan 27:6

27:6 You must build the altar of the Lord your God with whole stones and offer burnt offerings on it to the Lord your God.

[23:9]  ¹ tn Heb “evil.” The context makes clear that this is a matter of ritual impurity, not moral impurity, so it is “evil” in the sense that it disbars one from certain religious activity.