Albert Barnes Commentary Deuteronomy 23:2

"A bastard shall not enter into the assembly of Jehovah; even to the tenth generation shall none of his enter into the assembly of Jehovah." — Deuteronomy 23:2 (ASV)

A bastard - Probably, a child born of incest or adultery.

Even to his tenth generation - that is (see the next verse and Nehemiah 13:1), forever. Ten is the number of perfection and completeness.