In the beginning, at the very creation of the world, G-d set apart the 7th day with a blessing (Genesis 2:3). Therefore, we also say a blessing as we light the candles to welcome the Sabbath every Friday evening.
Baruch Atah Adonai Eloheinu Melekh HaOlam, Asher Kiddushanu B’mitzvotav V’tzivanu L’hiyot Or L’goyim V’natan Lanu Yeshua Meshicheinu Ha’or L’olam.
Blessed are you, O L-rd our G-d, Ruler of the Universe, Who has sanctified us by His commandments, and commanded us to be a light to the nations, and has given us Yeshua our Messiah, the Light of the World.
The first mention in the Torah of the Sabbath as a commandment is seen in Exodus 16:23, where the Children of Israel are commanded to gather twice as much manna on the 6th day, so that they will do no work gathering on the Sabbath. Later, Moses relays to them the Ten Commandments, including the fourth commandment, to remember the Sabbath day (Exodus 20:8-11).
The tradition of observing the first day of the week, Sunday, as a day of rest and worship was unknown until after the writing of the Bible, though Acts 20:7 records that early believers gathered after the conclusion of the sabbath to break bread and discuss their travels for the morning..