John Calvin 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 shall not enter. All agree that by the word ממזר, mamzer, a bastard is signified—one who is born of an uncertain father.

However, this term is interpreted in different ways. Some extend it to all bastards who spring from fornication, while others imagine that it refers only to those whose origin is doubtful and who are called vulgo geniti—namely, those whose mothers, through their base and common prostitution, have by their gross licentiousness caused their children to be born from this monstrous medley, as it were.

This second opinion I approve of most.

But by this symbol, God would admonish the seed of Abraham how exalted was its dignity, as separate from the polluted heathen.

Meanwhile, God would not altogether exclude these unhappy persons from the hope of salvation, although through no fault of their own they were unable to name their father. He only humbled them with a temporal punishment and desired that their example would be profitable to others.