Isaiah 56:4

4.For thus saith Jehovah. Now follows a confirmation; for the sincere worshippers of God, who keep the sabbaths and follow the righteousness of the Law, though they be “eunuchs,” (97) or labor under any other obstruction, shall nevertheless have a place in the Church. He appears to annihilate in this manner all the external marks (98) 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 hence we may readily infer that, when he spoke hitherto 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 think fit, but that which God declares to be pleasing and acceptable to himself. Wherefore both hypocrisy and inconsiderate zeal are here condemned, when God not only contrasts his own commandments with the inventions of men, but enjoins them earnestly to “take hold of his covenant.”