Albert Barnes Commentary Acts 10:28

"and he said unto them, Ye yourselves know how it is an unlawful thing for a man that is a Jew to join himself or come unto one of another nation; and [yet] unto me hath God showed that I should not call any man common or unclean:" — Acts 10:28 (ASV)

It is an unlawful thing. This was not explicitly commanded by Moses, but it seemed to be implied in his institutions and was, in any case, the common understanding of the Jews. The design was to keep them a separate people. To do this, Moses forbade alliances by contract or marriage with the surrounding nations, which were idolatrous (Deuteronomy 7:3–12).

The Jews perverted this command and explained it as referring to intercourse of all kinds, even to the exercise of friendly offices and commercial transactions .

Of another nation. Greek, Another tribe. It refers here to all who were not Jews.

God hath shewed me. Compare Acts 15:8-9. He had shown him by the vision (Acts 10:11–12).

Any man common or unclean. See the comments on Acts 10:14.

That no one was to be regarded as excluded from the opportunity of salvation, or be despised and abhorred.

The gospel was to be preached to all.

The barrier between Jews and Gentiles was to be broken down, and all were to be regarded as capable of being saved.