Belief 20 of 28 · Doctrines of the Christian Life
The Sabbath
The gracious Creator, after the six days of creation, rested on the seventh day and instituted the Sabbath as a memorial of creation. The fourth commandment requires the observance of this seventh-day Sabbath as the day of rest, worship, and ministry — from Friday sunset to Saturday sunset. Jesus is Lord of the Sabbath.
Genesis 2:2-3
On the seventh day God finished his work which he had done; and he rested on the seventh day from all his work which he had done. God blessed the seventh day, and made it holy, because he rested in it from all his work of creation which he had done.
Other Bible references for this belief
Genesis 2:1-3 · Exodus 20:8-11 · Exodus 31:13-17 · Leviticus 23:32 · Deuteronomy 5:12-15 · Isaiah 56:5,6 · Isaiah 58:13,14 · Ezekiel 20:12,20 · Matthew 12:1-12 · Mark 1:32 · Luke 4:16 · Hebrews 4:1-11
Look these up in your Bible app of choice for the full text — World English Bible (public domain), ESV, NIV, NKJV, NASB are all good.