Saturday is the Sabbath day – a day of rest according to the law of Moses – and the body of Jesus is in the tomb.
The Jewish leaders tell Pilate that Jesus claimed he would rise from the dead and that the disciples might try to steal the body and claim that Jesus had been raised and then “the last fraud will be worse than the first (Matthew 27:64). Pilate grants their request for a guard and has the tomb sealed.
The Sabbath began at sundown, so after the crucixion and burial of Jesus the Jews would have sought to rest for the Sabbath.
In addition to resting for the Sabbath what do you suppose the mood would have been among the followers of Jesus at this time?
Lakeshore Bible Study Online 
In addition to the Sabbath ceremonies I believe the disciples did have grief and fears and not fully knowing the prophecies were asking “What now?” “What’s going to happen to me and my family?” The uncertainty had to be tremendous. The Pharisee knew to guard the tomb for it was written he would rise the 3rd day. On this Sabbath day the disciples could not yet see that.
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