The feasts are God’s commandment for all who dwell on the Earth. (technically all of Torah is)
The feasts are the only way we can “watch” for his coming, and we are commanded to watch. (Revelation 3)
Once you are following his Torah, you are not a “gentile” any longer. That is the sole definition of Gentile: not abiding by Torah.
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I see a difference in Gods Law (written by God on stone dealing with our moral conduct and responsibilities) and the ordinances and ceremonial law (wrote by Moses dealing with material things) . Col. 2:14 - 17 indicates these (ordinances and ceremonial laws) are “shadow” things that expired at the cross. While following dietary and washings are good for the body, they no longer appear to be a requirement.