John Calvin Commentary Isaiah 56:4

"For thus saith Jehovah of the eunuchs that keep my sabbaths, and choose the things that please me, and hold fast my covenant:" — Isaiah 56:4 (ASV)

For thus says Jehovah. Now follows a confirmation: for the sincere worshippers of God, who keep the sabbaths and follow the righteousness of the Law, though they are “eunuchs,” or labor under any other obstruction, will nevertheless have a place in the Church. He appears to annihilate in this manner all the external marks in which alone the Jews gloried, for the high rank of the Church is not external, but spiritual. And although believers have no emblems of distinction in the eyes of the world, and are even despised and reproached, yet they rank high in the sight of God.

And choose the things that please me, and take hold of my covenant. With the “keeping of the Sabbath,” he connects obedience and adherence to “the covenant”; and from this we may readily infer that, when he spoke previously about the Sabbath, he had in view not an idle ceremony but perfect holiness. At the same time, he again lays a restraint on the children of God, not to make even the smallest departure from the injunction of the Law, for they are permitted to “choose,” not whatever they see fit, but that which God declares to be pleasing and acceptable to himself. Therefore, both hypocrisy and inconsiderate zeal are here condemned, when God not only contrasts his own commandments with the inventions of men, but also commands them earnestly to “take hold of his covenant.”