Also commentaries:
"We must conclude, therefore, that on the seventh day, on which God rested from His work, the world also, with all its inhabitants, attained to the sacred rest of God; that the sabbath day rest and the sabbath festivals of God were made a rest and sabbatic festival for His creatures, especially for man; and that this day of rest of the new created world, which the forefathers of our race observed in paradise, as long as they continued in a state of innocence and lived in blessed peace with our God and Creator, was the beginning and type of the rest to which the creation, after it had fallen from fellowship with God through the sin of man, received a promise that it should once more be restored through redemption, at its final consummation." Commentary on the Old Testament (1985 ed.; C.F. Keil and F. Delitzsch), page 70.
"The commencement of the kingdom of grace, in the sanctification of the Sabbath day (verse 3): The solemn observance of one day in seven, as a day of holy rest and holy work, to God's honor, is the indispensable duty of all those to whom God has revealed His holy Sabbaths. Sabbaths are as ancient as the world; and I see no reason to doubt that the Sabbath, being now instituted in innocency [before the fall], was religiously observed by the people of God throughout the patriarchal age. The Sabbath of the Lord is truly honorable, and we have reason to honor in obedience to him. The Sabbath day is a blessed day, for God blessed it, and that which he blesses is blessed indeed. God has promised, on that day, to meet us and bless us. The Sabbath day is a holy day, for God has sanctified it." Matthew Henry's Bible Commentary (1960 ed.), page 5.
"[Sabbath], the primary idea of which is to sit still, depicts Elohim as desisting from His creative labors, and assuming a posture of quiescent repose. The expression is a pure anthropomorphism. 'He who fainteth not, neither is weary' (Isaiah 40:28), can be conceived of neither as resting nor as needing rest through either exhaustion or fatigue. ... The blessing of the seventh day implied—1. That it was thereby declared to be the special object of the Divine favor. 2. That it was thenceforth to be a day or epoch of blessing for His creation. And—3. That it was to be invested with a permanence which did not belong to the other six days—every one of which passed away and gave place to a successor. [God] literally declared it holy ('and sanctified it'), for holy purposes. As afterwards Mount Sinai was sanctified (Exodus 19:23), or, for the time being, invested with a sacred character as the residence of God; and Aaron and his sons were sanctified, or consecrated to the priestly office; and the year of the jubilee was sanctified, or devoted to the purpose of religion, so here was the seventh day sanctified, or instituted in the interests of holiness, and as such proclaimed to be a holy day." [The author then goes on at length about how patriarchs observed the Sabbath] Josephus is quoted, "There is not any city of the Grecians, nor any of the barbarians, nor any nation whatsoever, whither our custom of resting on the seventh day hath not come." The Pulpit Commentary (1978 ed., Thomas Whitelaw), pages 35, 36.