The next reference to the Sabbath is in Exodus 16, when God sends the manna to feed the Children of Israel and ordains one day’s portion to be collected each day, but a double portion to be collected on the sixth day (Exodus 16:4-5). Moses explained (verses 23,26) that this was because:

"Tomorrow is the rest of the Holy Sabbath unto the Lord…. six days you shall gather it; but on the seventh day which is the Sabbath, in it there shall be none."

These arrangements were to be a test for Israel, as to whether they would walk in God’s law or not (verse 4).

When the people gathered the double portion on the sixth day, Moses reminded them of God’s instruction that the next day was to be the rest (Hebrew: shabbat, cessation) of the Holy (Hebrew: qodesh, set apart, separated) Sabbath unto the Lord. When some of the people went out on the seventh day, God protested to Moses: "How long refuse ye to keep My commandments and My laws? See, for that the Lord has given you the Sabbath. … So the people rested (Hebrew: shabbath) on the seventh day." (verses 28-30).

The key word and thought here is rest, as a point of strict obedience to God’s instructions.