John Calvin Commentary Isaiah 66:23

"And it shall come to pass, that from one new moon to another, and from one sabbath to another, shall all flesh come to worship before me, saith Jehovah." — Isaiah 66:23 (ASV)

From a month to his month, and from a Sabbath to his Sabbath. The Prophet again points out what the difference will be between the nature of the spiritual worship of God, which will be under the reign of Christ, and the physical worship that was under the Law. Sacrifices were offered every month at the new moon. There were Sabbaths, and other festivals, and solemn days, which they carefully observed.

But under the reign of Christ, there will be a constant and uninterrupted solemnity. For there are no fixed and stated days of sacrifices on which we must go to Jerusalem, or offer anything in one place or in another; rather, our offerings, festivals, and rejoicings are continued from day to day in unbroken succession. Yet, the Prophet alludes to the ancient custom of sacrifices, as we have already said, prophets are frequently accustomed to do.

So then, the Lord wishes to have “pure sacrifices” offered to Him daily (1 Peter 2:5), not such as were formerly offered under the Law or are now offered by Papists, who either rely foolishly on their ceremonies as if they were expiations of sin, or basely venture to sacrifice Christ, but spiritual sacrifices, so that we may reverence and adore God with a pure and sincere worship (John 4:24). Regarding the opinion held by some that this passage proves the abrogation of the Law and of ancient ceremonies, it does not seem to me to rest on sufficient grounds. It is indeed certain that those legal ceremonies have been set aside, and that can be gathered from this passage; but in proof of that point, I would choose to use other passages that contain stronger evidence. There is only here a contrast between the Sabbath and festivals which were celebrated under the Law, and the perpetual Sabbath that we have at the present day (Hebrews 4:9, 10).