Isaiah

If thou turn away thy foot from the sabbath, from doing thy pleasure on my holy day; and call the sabbath a delight, the holy of the Lord, honourable; and shalt honour him, not doing thine own ways, nor finding thine own pleasure, nor speaking thine own words:

Speak thou also unto the children of Israel, saying, Verily my sabbaths ye shall keep: for it is a sign between me and you throughout your generations; that ye may know that I am the Lord that doth sanctify you.

Wherefore the children of Israel shall keep the sabbath, to observe the sabbath throughout their generations, for a perpetual covenant.

Praise ye the Lord. Blessed is the man that feareth the Lord, that delighteth greatly in his commandments.

Moreover also I gave them my sabbaths, to be a sign between me and them, that they might know that I am the Lord that sanctify them.