The Mass of the First Sunday after Pentecost is always displaced by Trinity Sunday. It is commemorated in this Mass, and celebrated on a free day during the following week.
Introit: Tobias xii: 6
Blessed be the Holy Trinity, and undivided unity: We will give glory to Him because He has shown His mercy toward us. [Ps.] O Lord, our Lord, how wonderful is Thy name in all the earth! Glory be.... Blessed be....
Almighty and everlasting God, who hast given to Thy servants grace in the confession of the true faith to acknowledge the glory of the eternal Trinity, and in the power of Thy majesty to worship the Unity; grant that by steadfastness in the same faith we may evermore be defended from all adversities. Through our Lord....
Collect (of the First Sunday after Pentecost):
O God, the strength of all those who put their trust in Thee, mercifully hear our prayers, and because through the weakness of our mortal nature we can do nothing without Thee, grant us the help of Thy grace, that in fulfilling Thy commandments, we may please Thee both in will and deed. Through our Lord.
Epistle: Romans xi: 33-36
A reading from the Epistle of blessed Paul the Apostle to the
Gradual: Daniel iii: 55-56
Blessed art Thou, O Lord, that beholdest the depths and sittest upon the Cherubim. Blessed art Thou, O Lord, in the firmament of heaven, and worthy of praise forever.
Alleluia, alleluia. Blessed art Thou, O Lord, the God of our fathers, and worthy to be praised forever. Alleluia.
Gospel: Matthew xxviii: 18-20
+ The continuation of the Holy Gospel according to Matthew.
At that time, Jesus said to His disciples: "All power in heaven and on earth has been given to me. Go, therefore, and make disciples of all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost, teaching them to observe all that I have commanded you; and behold, I am with you all days, even unto the consummation of the world."
Blessed be God the Father, and the only begotten Son of God, and also His Holy Ghost; because He has shown His mercy to us.
Sanctify, we beseech Thee, O Lord our God, by the invocation of Thy holy name, the victim of this oblation, and by its means make us an eternal oblation to Thee. Through our Lord....
Secret (Of the Sunday):
We beseech Thee, O Lord, graciously receive our offerings devoted to Thee, and grant that they may ever be a source of help to us. Through our Lord....
Communion: Tobias xii: 6
We bless the God of heaven, and before all living beings we will praise Him; because He has shown His mercy to us.
May the reception of this Sacrament, O Lord our God, and the confession of the holy and eternal Trinity, and of Its undivided unity, profit us unto the salvation of soul and body. Through our Lord....
Postcommunion (Of the Sunday):
Grant, we beseech Thee, O Lord, that we who have been replenished with such great gifts, may both receive their saving benefits, and may never cease from Thy praise. Through our Lord....