God has commanded that we do our heavy cooking—roasting, baking, boiling, broiling—on the day before the Sabbath. The command to do this is clear. It is interesting to think about how frequently men think that "what God says" does not really apply to them or that it does not matter. What they are doing is presuming to add or subtract from His Word.
God said that He was going to give Israel a test (Exodus 16:4). The test dealt with keeping the fourth commandment, the Sabbath. He wanted to see whether they would obey Him. He then commanded them to prepare for it, so that they could pass the test!
Does God mean what He says? He is serious enough about our keeping of the Sabbath that He added an additional commandment to make sure that we are prepared to keep it and thus pass the test. The test, then, is not whether we know about the Sabbath but how we keep it. To keep the Sabbath, we must prepare for it.
Whether or not we will live by God's Word depends upon our faith because, in reality, the test is of our faith. It tests whether we believe what God says. If we are depending only upon our eyes—our senses—we are quite limited. There are things we cannot see or hear that are very important to God. By appearance, the Sabbath is no different from any other day of the week. This means everybody is confronted by a test of faith in keeping it, and preparation is a key to keeping it properly.