In the washing of the feet, we catch a glimpse of what Jesus does and what he is. He, who is the Lord, stoops to our level. He lays aside the robes of his kingship and becomes a slave, standing at the door and performing the duty of a slave -- the washing of the feet. That is the meaning of his whole life and Passion: the he bends to wash our dusty feet, to wash away the dust of humanity, and, in his exceedingly great love, washes us clean. The purpose of this menial task of washing the feet was to make the guests fit to appear at table, to appear in company, so that they could sit together at table. Jesus Christ makes us, as it were, fit to appear at table and in company both before God and before one another; we, who are not fit to appear before God, are received by Jesus. He wears, so to speak, the garment of our wretchedness and, by taking us with him, makes us fit to stand in the presence of God; we have gained access to God. We are washed by letting ourselves be drawn into his love. This love means that God receives us unconditionally even when we are not capable and are not worthy of it, because he, Jesus Christ, transforms us and becomes our Brother.
-- Cardinal Joseph Ratzinger.
Excerpt from Co-Workers of the Truth.