Saturday is the Jewish sabbath day – a day of rest. And so Christ himself ‘rests’ in his tomb while his disciples hide in fear. 3 days he lies in the tomb as they think the worst – that all is lost. A reminder that even crushing defeat cannot stop God – but that things happen in His time.
However, Christ is not inactive. It is long thought this day he descended to Hell and freed the holy souls trapped there before they had a savior. Before Christ, Jews believed all souls went to Sheol. The Harrowing of Hell is depicted in many early icons such as this one by Fra Angelico (1400’s) in one of his fellow monks cels in Florence.