At the Last Supper, Christ celebrated both the Jewish and the Christian Passover, ‘both the Passover that was the type and the Passover that was the reality. Christ was doing exactly what an artist does when on the same canvas he first draws an outline and puts in the shading, and then adds the actual colors. At the very same table, He both sketched out the Passover that was a type and added in the true Passover.’

“The Divine Liturgy – A Commentary in the Light of the Fathers” by Hieromonk Gregorios
Quotations from St. John Chrystostom