Why do we need to have a day of rest? It's one of the 10 commandments, but is it really that important?

The Proving of Christians

We, at Harmony, believe the whole Bible is the holy, inspired, word of God.  We confess in accordance with Holy Scripture and with the Holy Spirit’s help, that Jesus Christ is the one and only Son of God. Confession of Jesus as the Son is Essential, not a matter of personal opinion."