Christ is both the way and the door. Christ is the staircase and the vehicle, like the throne of mercy over the Ark of the Covenant, and the mystery hidden from the ages. A man should turn his full attention to this throne of mercy, and should gaze at him hanging on the cross, full of faith, hope and charity, devoted, full of wonder and joy, marked by gratitude, and open to praise and jubilation. Then such a man will make with Christ a pasch, that is, a passing-over. Through the branches of the cross he will pass over the Red Sea, leaving Egypt and entering the desert. There he will taste the hidden manna, and rest with Christ in the sepulchre, as if he were dead to things outside. He will experience, as much as is possible for one who is still living, what was promised to the thief who hung beside Christ: Today you will be with me in paradise.
For this passover to be perfect, we must suspend all the operations of the mind and we must transform the peak of our affections, directing them to God alone. This is a sacred mystical experience. It cannot be comprehended by anyone unless he surrenders himself to it; nor can he surrender himself to it unless he longs for it; nor can he long for it unless the Holy Spirit, whom Christ sent into the world, should come and inflame his innermost soul. Hence the Apostle says that this mystical wisdom is revealed by the Holy Spirit.
- St. Bonaventure (source: here)