Isaiah 56:
[3] Neither let the son of the stranger, that hath joined himself to the LORD, speak, saying, The LORD hath utterly separated me from his people: neither let the eunuch say, Behold, I am a dry tree.
[4] For thus saith the LORD unto the eunuchs that keep my sabbaths, and choose the things that please me, and take hold of my covenant;
[5] Even unto them will I give in mine house and within my walls a place and a name better than of sons and of daughters: I will give them an everlasting name, that shall not be cut off.
Answer, IF they keep MY COVENANTS, keep MY SABBATHS, and CHOOSE THE THINGS THAT PLEASE ME, God says. Where would these eunuchs and son of the stranger FIND these things? THROUGH ISRAEL. It was THROUGH ISRAEL they would be saved.
This is important. They, on their own, could not approach God. ONLY through Israel did they have ANY hope of salvation.