Q: Very good comment on Isa 56 about Jesus as Salvation [see our Q&A on Isaiah 56]. But what about the context:
has to offer also Sabbath-keeping as a sign of the new covenant that is brought about by the Messiah (verse 8 "to HIM" will be gathered all). Do you agree that the Sabbath is also the sign of the new covenant for non-Jews, for all Christians? –Jens S. Israel
A: Thank you for bringing up the issue of Sabbath with regard to Isa. 56. As you correctly point out, this is a key element in the chapter. I'm not sure exactly what you mean by Sabbath-keeping being a “sign of the new covenant” for Israel, since Sabbath-keeping is usually considered a sign of the old covenant as it specifically says in Exo. 31:13; Eze. 20:12. But if you simply mean that it continues as part of the practice of Jewish believers in Jesus, this is certainly true.
With regard to Isa. 56:8 ("The Lord GOD, who gathers the banished ones of Israel, declares, 'Yet others I will gather to him, to those already gathered.'"), the phrase "yet others will I gather to him" is a reference back to Israel in the same verse, and as a result, is often translated for clarity “to them.” This is how Jesus understood it when he alluded to this verse in John 10:16, speaking of the "other sheep" that were to be added to the Jewish people who had already believed in him.
The foreigners (or literally the “sons of a foreigner”) of Isa. 56:6 are some of these “other sheep” that are to be gathered (in vs. 8). But notice carefully the language used for these foreigners with regard to the Sabbath. The Jewish eunuchs in vs. 4 are instructed to “keep my sabbaths.” But for the Gentile foreigners in vs. 6, they are instructed to “keep from dishonoring the Sabbath.” What’s the difference?
The plural “sabbaths” in vs. 4 instructs Jewish eunuchs not only to observe the weekly Sabbaths, but also to observe all the other festival sabbaths of Israel as well. In other words, Jewish eunuchs are instructed to observe the Law of Moses completely.
But nothing about these other sabbaths is mentioned in the instructions given to Gentile foreigners, nor are they told to observe the weekly Sabbath as the Jewish people do, but rather they are only told to avoid dishonoring the Sabbath, which is quite different.
This difference is key in dealing with your question about the Sabbath for non-Jewish believers in Jesus. The Council of Acts 15 decided that Gentile believers should not become proselytes (converts) to Judaism, and as a result, Sabbath-keeping was not required of them. Instead, the requirements outlined in Acts 15 are similar to the rabbinic idea of the Seven Laws of Noah. Neither system of requirements for Gentiles included keeping the weekly Sabbath in the Jewish manner. This is why there is little evidence of Sabbath-keeping in the Gentile portions of the early church. There is, however, evidence of respect for the Sabbath, especially in the Eastern Church. Just as Isaiah instructed, they kept from dishonoring the Sabbath, even though they did not observe it in the Jewish way.