The Gospel reading from St. Matthew's Gospel presents the fulfillment of God's plan to redeem humanity. The Passion of our Lord is the remedy for our sin. It was accomplished through the humility of God as St. Paul writes in the second reading from Philippians,

Christ Jesus, though he was in the form of God,
did not regard equality with God
something to be grasped.
Rather, he emptied himself,
taking the form of a slave,
coming in human likeness;
and found human in appearance,
he humbled himself,
becoming obedient to the point of death,
even death on a cross.

Readings:

Isaiah 50:4-7
Psalm 22:8-9, 17-20, 23-24
Philippians 2:6-11
Matthew 26:14-27:66

Here are a few commentaries on these readings:

In Agony Until the End of the World - Pontifical Household preacher, Capuchin Father Raniero Cantalamessa (Courtesy of Zenit)

St. Charles Borromeo Lectionary Site (PDF)

All Is Fulfilled - St. Paul Center for Biblical Theology

The Victory of Humility - The Crossroads Initiative