Sforno on Deuteronomy 23:15/ספורנו על דברים כ״ג:ט״ו

1והיה מחניך קדוש, both free of ritual impurities as well as from repulsive things, even though not ritually impure.

2ולא יראה בך ערות דבר, a description of Jewishly unfit offspring or some other impediment to G’d’s Shechinah resting over the Jewish people, as our sages (Kidushin 70) said: “the Shechinah rests only over the ancestrally pure Jewish families.” They added that anyone who can trace his ancestry to King David, (folio 76) by his ancestor having been a soldier in his army, is acceptable without question.

3מאחריך, if you were to turn your rear to Him by ignoring these laws and thus insulting Him.