Targum Onkelos: And the Lord saw all that He had made, and, behold, it was very steadfast. And it was evening, and it was morning, Day the Sixth.
Rashi: the sixth day: Scripture added a “hey” on the sixth [day], at the completion of the Creation, to tell us that He stipulated with them, [“you were created] on the condition that Israel accept the Five Books of the Torah.” [The numerical value of the “hey” is five.] (Tanchuma Bereishith 1). Another explanation for “the sixth day” : They [the works of creation] were all suspended until the “sixth day,” referring to the sixth day of Sivan, which was prepared for the giving of the Torah (Shab. 88a). [The“hey” is the definite article, alluding to the well-known sixth day, the sixth day of Sivan, when the Torah was given (ad loc.).]
Rambam: God confirmed all that God had done in its existence in God’s will, even the evil within creation — death, the evil impluse, and punishment — for evil requires the existence of good. There was one revolution of the diurnal sphere; the sixth day.
Ibn Ezra: God understood that all that God had created was very good. The diurnal sphere revolved once, day blended into evening and night blended into dawn, the sixth day from day one.
Diurnal sphere: See commentary on verse 5