3 Therefore, my brethren, I would desire to have impressed this upon your hearts: if you wish to live in a pious and Christian manner, cling to Christ according to that which He became for us, that you may arrive at Him according to that which is, and according to that which was. He approached, that for us He might become this; because He became that for us, on which the weak may be borne, and cross the sea of this world and reach their native country; where there will be no need of a ship, for no sea is crossed.
It is better then not to see with the mind that which is, and yet not to depart from the cross of Christ, than to see it with the mind, and despise the cross of Christ. It is good beyond this, and best of all, if it be possible, that we both see whither we ought to go, and hold fast that which carries us as we go. This they were able to do, the great minds of the mountains, who have been called mountains, whom the light of divine justice pre-eminently illuminates; they were able to do this, and saw that which is.
For John seeing said, “In the beginning was the Word, and the Word was with God, and the Word was God.” They saw this, and in order that they might arrive at that which they saw from afar, they did not depart from the cross of Christ, and did not despise Christ's lowliness. But little ones who cannot understand this, who do not depart from the cross and passion and resurrection of Christ, are conducted in that same ship to that which they do not see, in which they also arrive who do see.
Source: Tractates on the Gospel of John (New Advent)