The theologian Edward Schillebeeckx described Christ as the primordial sacrament. What does that mean?
Edward Schillebeeckx was a Dominican priest, born in Belgium in 1914, taught theology at the University of Nijmegen in the Netherlands, and was influential at the Vatican Council. He was a very prolific writer. He expired in 2009.
William J Hill OP, a fellow Dominican, wrote a "non-technical" summary of Schillebeeckx work in this field called "Christ, the Sacrament of the Encounter with God". Google William J Hill Christ Sacrament Encounter
Fundamental is the concept of Encounter.
An Encounter with God is always sacramental, in that it must involve some visibility or physical expression, capable of human perception; and yet that this must point to, signify, and be, a reality beyond our conception. Encounter as a human confrontation can only happen through physical expression.
Jesus, when on Earth, was a human being, outwardly and visibly, and truly. Yet He was also the Manifestation of God, His hidden Reality as the Express Image of the Father. HIs Redemptive Incarnation was a sign, and an instrument of God's love for mankind, delivering God's grace.
The very existence of Christ makes possible encounter with God. This applies to every detail of His life, but most particularly to His Passion and Death. This revealed both God's will to save, and Christ's love for His Father. The Death of Our Lord Jesus Christ both signifies and causes, is sign and effect, of the Reconciliation of Man to God.
Now that Christ is in Glory, His continuing action in the World demands a tangible prolongation of His Incarnation. This is the Church, and Christ acts, through the Church, in and by the Sacraments. The Sacraments signify what they effect, and effect what they signify, but more importantly they are Acts of Christ. Though done at one time and in one place, they transcend both time and place.
Christ is the greatest and original Sacrament, so primordial; and also primordial in that all other sacraments derive from His actions and so from Him.