While preparation for the Sabbath is to be made all through the week, Friday is to be the special preparation day.

Through Moses the Lord said to the children of Israel: “Tomorrow is the rest of the holy Sabbath unto the Lord: bake that which ye will bake today, and seethe that ye will seethe; and that which remaineth over lay up for you to be kept until the morning.” “And the people went about, and gathered it [the manna], and ground it in mills, or beat it in a mortar, and baked it in pans, and made cakes of it.” Exodus 16:23; Numbers 11:8. There was something to be done in preparing the heaven-sent bread for the children of Israel. The Lord told them that this work must be done on Friday, the preparation day. 5T 354

This was a test to them. God desired to see whether or not they would keep the Sabbath holy.

This direction from the lips of Jehovah is for our instruction. The Bible is a perfect guide, and if its pages are prayerfully studied by hearts willing to understand, none need err upon this question.