On the sixth day. That a period of seven days was known to the Hebrews as a week appears from the story of Jacob and Laban (Genesis 29:27). But there is no distinct evidence that the year was as yet divided into weeks, much less that the several days of the week were as yet distinguished as the first, second, third day, etc.
"The sixth day," here probably means (as Kalisch says), "the sixth day after' the first supply of the manna. They shall prepare. The preparation would be, first, by measurement (Exodus 16:18), and then by pounding and grinding (Numbers 11:8).
It shall be double. Some commentators suppose that in these words is implied an order that on the sixth day they should set themselves to gather a double quantity. But the natural meaning of the words is, that, having gathered the usual quantity, they should find, when they measured it, that, by miracle, the supply sufficient for one day was multiplied, so as to suffice for two.
(So Kalisch, Knobel, Kurtz, and others.) This view is in harmony with Exodus 16:18, which tells of a miraculous expansion and diminution of the manna after it had been gathered, and with Exodus 16:22, which shows us "the rulers" surmised by the miracle of the sixth day.