Why was the Sabbath instituted during the manna gathering?
The Sabbath was instituted so Israel would gather twice as much manna on the sixth day, Friday, providing enough for the seventh day and preventing any need to work then. This arrangement ensured they could rest on the seventh day without gathering food.
Les explains that after Exodus chapter 16, where the people had been given the manna, the Sabbath was instituted in connection with the manna gathering. They were to pick up twice as much on the sixth day, Friday, in order to have enough so that they would not have to work on the seventh day. This allowed them to rest on the Sabbath rather than gather manna.