This is the day that Christ gave us the ordinance of the Lord's Supper and the tradition of foot-washing.

This is the night that we are given the symbols of Christ's submission to our need for a Saviour and the symbol of servant-leadership.

When he had washed their feet and put on his outer garments and resumed his place, he said to them,  "Do you understand what I have done to you?  You call me Teacher and Lord, and you are right, for so I am. If I then, your Lord and Teacher, have washed your feet, you also ought to wash one another’s feet. For I have given you an example, that you also should do just as I have done to you. Truly, truly, I say to you, a servant is not greater than his master, nor is a messenger greater than the one who sent him. If you know these things, blessed are you if you do them.  (John 13: 12-17 ESV)

Christ was the greatest sovereign who had every walked the earth - God Incarnate; Immanuel.  Yet He gave this example in of service in His leadership.

Now as they were eating, Jesus took bread, and after blessing it broke it and gave it to the disciples, and said, "Take, eat; this is my body." And he took a cup, and when he had given thanks he gave it to them, saying, "Drink of it, all of you, for this is my blood of the covenant, which is poured out for many for the forgiveness of sins. I tell you I will not drink again of this fruit of the vine until that day when I drink it new with you in my Father’s kingdom." (Matt. 26: 26-29 ESV)

and we are reminded of this later in Scripture:

Husbands, love your wives, as Christ loved the church and gave himself up for her, that he might sanctify her, having cleansed her by the washing of water with the word, so that he might present the church to himself in splendor,without spot or wrinkle or any such thing, that she might be holy and without blemish.  In the same way husbands should love their wives as their own bodies. He who loves his wife loves himself. For no one ever hated his own flesh, but nourishes and cherishes it, just as Christ does the church, because we are members of his body (Eph 5:25-30 ESV)