According to the Bible, the origin of the Sabbath is the creation of the world-
“And God blessed the seventh day and declared it holy, because on it God ceased from all the work of creation that He had done.” (Genesis 2-3)
The Bible proscribes observance of the Sabbath-
“Remember the Sabbath day and keep it holy.” (Exodus 20-8)
The observance of the Sabbath is reported-
“And the Children of Israel observed the Sabbath, to make the Sabbath for their generations an eternal covenant. Between Me and the Children of Israel it is a sign forever…” (Exodus 31-16)
The text of the Sabbath Ostraca is as follows-
Look, I’m sending you the vegetables tomorrow. Get there before the boat comes in – on account of the the Sabbath – so they won’t be spoiled. I swear to God, if you don’t, I’ll kill you! Don’t trust Meshullemet or Shemayah to take care of it.
Trade the barley for me. Try to get a lamb… I swear to God, if you don’t, you’ll have to… yourself.
As for the… you sent in exchange for the wine, I have sent it all on to them (?). If Meshullemet doesn’t get here, what will you say?
May we see each other soon!