Holy and Great Thursday. Washing the feet of the Apostles. Wall painting of the Panagia Assinou in Nikitari, Cyprus. 1105. On this day, Holy and Great Thursday, according to the order which our Holy Fathers inherited from the Holy Apostles, and the Holy Gospels, we celebrate four events: the Holy Washing of the Disciples' feet, the Mystical Supper (the institution of the Holy Mystery of the Eucharist, which we celebrate to this day), the Lord's Agony in the Garden, and His Betrayal.

And as they were eating, Jesus took bread, and blessed it, and brake it, and gave it to the disciples, and said, Take, eat; this is my body. And he took the cup, and gave thanks, and gave it to them, saying, Drink ye all of it; For this is my blood of the new testament, which is shed for many for the remission of sins.

Mt. 26:26–28