For those of you that don't believe the Sabbath was instituted from creation but was only given at Mt Sinai, how do you explain that the Israelites kept the Sabbath after the Exodus before arriving at Mt Sinai? If this was something new to them, how did Moses know beforehand what the Sabbath was and how to keep it? Of all the accounts of the murmurings of the Israelites, why was there no record of them complaining about this strange new rule, especially after some had been killed for violating it? Would God so punish someone before they even knew about this Law?