Isaiah 56:3

"Neither let the foreigner, that hath joined himself to Jehovah, speak, saying, Jehovah will surely separate me from his people; neither let the eunuch say, Behold I am a dry tree. For thus saith Jehovah of the eunuchs that keep my sabbaths, and choose the things that please me, and hold fast my covenant: Unto them will I give in my house and within my walls a memorial and a name better than of sons and of daughters; I will give them an everlasting name, that shall not be cut off."

Notice that the words "hold fast my covenant" in Isaiah 56:4 are the same as "keeping the sabbath days," thus a reference to their keeping the whole law of Moses.

Why this special reference to "foreigners" and to "eunuchs"? Isaiah had already prophesied, "That a certain number of the seed of Hezekiah would serve as eunuchs in the royal palace of the king of Babylon" (2 Kings 20:18); and Daniel and his three faithful companions were among those who thus served.[3] There were doubtless many others of the captives who suffered the same cruel treatment. The words given here were for the encouragement of all such persons. The foreigners were included because of the likelihood that some of the Babylonians would, through human kindness, become attached to God's people and join them; and these words were also extended to encourage them.

This meant that, "The law of Deuteronomy 23:1, regarding the exclusion of eunuchs and foreigners, would be abrogated,"[4] during the times of the captivity for those who "kept the covenant."

REGARDING THAT NEW NAME

"A memorial name, a name better than of sons and of daughters ... an everlasting name that shall not be cut off ..." (Isaiah 56:5). The name here referred to is the name, Christian. Isaiah here prophesied that the name would be given, not by God's enemies, but by himself within his house and within his walls, that is, within the church, the church being the only "house" God ever had, certainly, not the Jewish Temple, which, from the beginning was contrary to God's will. Isaiah also prophesied that this memorial name would be "a new name" (Isaiah 62:2), and a name which the "mouth of the Lord" would give, and that it would be given after the "kings and the Gentiles had seen the righteousness of God," that is, after the Church of Messiah had been established and after Gentiles were accepted into it. (See the discussion of the name "Christian," in Vol. 5, (Acts) of my New Testament Series of Commentaries, pp. 333-336.)