St. Thomas Aquinas on the seamless garment:
He says, also his tunic, that is, they took that along with his other garments. But the tunic was without seam, woven from top to bottom. He says that it was without a seam to indicate its unity. Some say this shows how valuable it was. On the other hand, Chrysostom says that the Evangelist says this to suggest that it was common and ordinary; for in Palestine the poor wear clothing made from many pieces of cloth, one sewn over another: "For you know the grace of our Lord Jesus Christ, that though he was rich, yet for your sake he became poor" (2 Cor 8:9).
As for the mystical interpretation, this passage can be referred to the mystical body of Christ. Then Christ's garments are divided into four parts because the Church is spread over the four parts of the world: "As I live, says the Lord, you shall put them all on as an ornament, you shall bind them on as a bride does" (Is 49:18). The tunic without seam, which was not divided, indicates charity, because the other virtues are not united by themselves, but by another, because all of them are directed to the ultimate end, and it is charity alone which unites us to this end. While it is faith which makes known our ultimate end, and by hope we tend toward it, only charity unites us to it: "And above all these put on love, which binds everything together" (Col 3:14).
The tunic is said to be woven from the top because charity is above, at the top, of all the other virtues: "I will show you a still more excellent way" (1 Cor 12:31); "To know the love of Christ which surpasses knowledge, that you may be filled with all the fullness of God" (Eph 3:19). Or, it is woven from the top because our charity does not come from ourselves, but from the Holy Spirit: "God's love has been poured into our hearts through the Holy Spirit which has been given to us" (Rom 5:5). The tunic woven from the top can also signify the real body of Christ, because the body of Christ was formed by a higher power, one from the top, by the Holy Spirit "That which is conceived in her is of the Holy Spirit" (Mt 1:20).
St. Augustine writes on the blood and water which flowed from the side of Jesus:
"Then came the soldiers, and broke the legs of the first, and of the other who was crucified with Him. But when they came to Jesus, and saw that He was dead already, they broke not His legs: but one of the soldiers with a spear laid open His side, and forthwith came there out blood and water."
A suggestive word was made use of by the evangelist, in not saying pierced, or wounded His side, or anything else, but "opened;" that thereby, in a sense, the gate of life might be thrown open, from whence have flowed forth the sacraments of the Church, without which there is no entrance to the life which is the true life. That blood was shed for the remission of sins; that water it is that makes up the health-giving cup, and supplies at once the laver of baptism and water for drinking.
This was announced beforehand, when Noah was commanded to make a door in the side of the ark, Genesis 6:16 whereby the animals might enter which were not destined to perish in the flood, and by which the Church was prefigured. Because of this, the first woman was formed from the side of the man when asleep, Genesis 2:22 and was called Life, and the mother of all living. Genesis 3:20 Truly it pointed to a great good, prior to the great evil of the transgression (in the guise of one thus lying asleep). This second Adam bowed His head and fell asleep on the cross, that a spouse might be formed for Him from that which flowed from the sleeper's side.
O death, whereby the dead are raised anew to life! What can be purer than such blood? What more health-giving than such a wound?
John Chrysostom meditates on the death of Jesus:
But do thou consider, I pray, how even on the cross He did everything without being troubled, speaking with the disciple concerning His mother, fulfilling prophecies, holding forth good hopes to the thief.
Yet before He was crucified He appears sweating, agonized, fearing. What then can this mean? Nothing difficult, nothing doubtful. There indeed the weakness of nature had been shown, here was being shown the excess of Power.
Besides, by these two things He teaches us, even if before things terrible we be troubled, not on that account to shrink from things terrible, but when we have embarked in the contest to deem all things possible and easy. Let us then not tremble at death.