Ezra 6:21 - Joseph Benson’s Commentary on the Old and New Testaments

All such as had separated themselves unto them, &c. Had left their country, and the superstitions and vices of it; had become proselytes to the Jewish religion, and cast in their lot with the Israel of God, professing an entire subjection to the law of Moses. Such, and only such, might eat of the passover, Exodus 12:48-49. From the manner in which the sacred writer expresses himself here, it would seem as if there were many proselytes, who forsook their heathenish customs, and were brought to the knowledge and worship of the true God, influenced, probably, by the encouragement which Cyrus and Darius had given to the Jewish religion. People of all nations, it must be observed, till proselyted, were accounted by the Jews polluted both in body and mind, because of their worshipping false gods, and not abstaining from the things which were accounted unclean by the law of Moses. The description here given of proselytes to Judaism may serve to characterize converts to the true religion in every age: they separate themselves from the filthiness of sin, and fellowship with sinners; join themselves to the Israel of God in conformity and communion, and set themselves to seek the God of Israel: and those that do so in sincerity, though strangers and foreigners, are welcome to eat of the gospel-feast, as fellow-citizens with the saints, and of the household of God.