6 And foreigners who bind themselves to the LORDto minister to him, to love the name of the LORD, and to be his servants, all who keep the Sabbath without desecrating it and who hold fast to my covenant—

Read Isaiah 56:6 Using Other Translations

Also the sons of the stranger, that join themselves to the LORD, to serve him, and to love the name of the LORD, to be his servants, every one that keepeth the sabbath from polluting it, and taketh hold of my covenant;
"And the foreigners who join themselves to the LORD, to minister to him, to love the name of the LORD, and to be his servants, everyone who keeps the Sabbath and does not profane it, and holds fast my covenant--
“I will also bless the foreigners who commit themselves to the LORD, who serve him and love his name, who worship him and do not desecrate the Sabbath day of rest, and who hold fast to my covenant.