Holy Trinity Sunday

Feast of the Most Holy Trinity
fragments from "Devout Instructions" by Fr. Goffine (1896 Benziger Brothers, Printers of the of the Holy Apostolic See)

Every Sunday is dedicated to the worship of the Triune God, and is called accordingly the Lord's day; but the first Sunday after Pentecost is appointed by the Church a special feast of the Most Holy Trinity, because this mystery, as the fundamental doctrine of the Christian religion, began at once to be preached by the apostles, as soon as they had been enlightened and strengthened by the descend of the Holy Ghost. What thoughts and affections should occupy our minds on this feast?
Although the mystery of the Trinity is incomprehensible to us, we must consider:
1. That God would cease to be God, if our limited understanding were capable of penetrating the substance of His nature.
2. The mystery of the Blessed Trinity, though incomprehensible to our intellect, is yet not without fruit in our hearts.
The records of revelation show us God the Father as our Creator, God the Son as our Redeemer, God the Holy Ghost as our Sanctifier; and should not this move us to a child-like gratitude towards the blessed Trinity? In praise of the Most Holy Trinity, the Church sings at the Introit of the Mass, "Blessed be the Holy Trinity and undivided Unity; we will give glory to Him, because He hath shown his mercy to us. O Lord, our Lord, how wonderful is Thy name in all the earth." Glory be to the Father, etc.
PRAYER
O almighty and eternal God, Who hast created Thy servant to acknowledge the glory of the eternal Trinity, in the confession of the true faith, and to adore the unity in the power of Thy majesty, we beseech Thee, that by firmness in the same faith, we may be ever protected from all adversities. Through Jesus Christ, etc.
EPISTLE Rom.xi. 33-36
Oh, the depth of the riches of the wisdom and of the knowledge of God! How incomprehensible are His judgments, and how unsearchable His ways! For who hath known the mind of the Lord? Or who hath been His counselor? Or who hath first given to Him, and recompense shall be made Him? For of Him, and by Him, and in Him, are all things: to Him be glory forever. Amen.
Explanation
The ground of St. Paul's admiration in this epistle is the unfathomable wisdom and love of God, by which He permitted the Jews and heathen to fall into unbelief, that He might have mercy on all, and make all perceive that they were justified, not through their merits, but only through His grace. But the Church make use of this words to express her reverent admiration for the greatness of the mystery of the all Holy Trinity. Though we can neither measure nor comprehend this mystery, yet no man of sound reason will hesitate to believe it, if he considers that it is most plainly revealed by God; that as God, the Infinite, cannot be comprehended by the spirit of man, so also He can reveal more than we can understand; and that, finally, there are many things in man himself, and in nature, which we acknowledge as true, but cannot comprehend. Besides, does not our holy religion assure us, that one day we shall behold face to face the Infinite Whose image is now reflected dimly in the mirror of nature? Let us add hope, therefore, to our faith, and if true and sincere love be based upon these two, our understanding and heart will have abundant consolation in regard to this great mystery.
GOSPEL Matt. xxviii. 18-20
At that time Jesus said to His disciples: all power is given to Me in heaven and in earth; going therefore teach ye all nations: baptizing them in the name of the Father, and of the Son, and of the Holy Ghost: teaching them to observe all things whatsoever I have commanded you: and behold I am with you all days, even to the consummation of the world.
What command does our Saviour give in this gospel? He commands his apostles to teach all nations, and to baptize them.
Is Baptism a sacrament?
Yes, for by it we receive the grace of God, through an outward sign instituted by Christ.
What is the outward sign?
Pouring water on the head of the person to be baptized and pronouncing at the same time the words: "I baptize you in the name of the Father and of the Son and of the Holy Ghost."
What is the effect of the grace of Baptism?
Through water and the Holy Ghost, the baptized person is cleansed from original sin, and from all actual sins, if he has committed such; is spiritually new-born, and made a child of God and a joint-heir with Christ (John iii.6; Rom. vii. 17).
What is the use of sponsors?
1. In the name of the child, they express the desire to be baptized, and make the profession of faith, together with the promise to live according to the doctrine of Christ.
2. In case the parents should die, or neglect their duty, the god-parents may provide for the instruction of the children.
3. They are witnesses that such a person has been baptized.

THE MOST HOLY TRINITY
Who is God?
God is infinite being, of all possible perfections, the most sublime and excellent of all goods, existing from all eternity, and containing within Himself the principle of His own being and substance; from Whom all other things have received their existence and life, "for of Him, and by Him, and in Him are all things" (Rom. xi. 36).
What is the blessed Trinity?
It is this one God, Who is one in nature and threefold in person, - the Father, Son and Holy Ghost.
Is each of these persons God?
Yes, for each possesses the divine nature and substance
Is any of these three persons older, more powerful, or greater than another?
No; they are all three, from eternity, equal in power, sublimity, and majesty, and must therefore be equally adored.
From Whom is the Father?
From Himself, before all eternity.
From Whom is God the Son?
The Son is begotten of the Father before all ages.
From Whom is God the Holy Ghost?
He proceeds from the Father and the Son.