In the Mass, we use the wonderful words Jesus taught us as we pray the "Our Father". The Catholic "Our Father" does not include some words heard in Parliament House or non-Catholic denominations, "For thine is the kingdom, the power and the glory, now and forever", although we do say something similar when we pray the Our Father at Mass; after the Priest has spoken we say, "For the kingdom, the power and the glory are yours, now and forever." When discussing prayer with His disciples, Our Lord said,
This is how you are to pray: 'Our Father in heaven, hallowed be Your name, Your kingdom come, Your will be done on earth as it is in heaven. Give us today our daily bread and forgive us the wrong we have done as we forgive those who wrong us. Subject us not to trials but deliver us from the evil one' (Matthew 6:9-13).

A similar version is found in Luke 11:2-4. Neither version includes the ending, " For thine......." The "For thine......." is technically termed a doxology, a short hymn of praise. The Jews often used doxologies to conclude prayers at the time of Our Lord.

In the early Church, the Christians living in the eastern half of the Roman Empire added the doxology "for thine...." to the Gospel text of the Our Father when reciting the prayer at Mass. Evidence of this practice is also found in the "Didache" (Teaching of the Twelve Apostles), a first century manual of morals, worship and doctrine of the Church. also, when copying the Scriptures, Greek scribes sometimes added the doxology onto the original Gospel text of the Our Father.

In the western half of the Roman Empire and in the Latin rite, st, Jerome (d. 420) attested to the usage of the Our Father in the Mass. The Church saw in this perfect prayer which our Lord gave us a proper means of preparing for Holy Communion. Interestingly, the English wording of the Our Father that we use today reflects the version mandated for use by Henry VIII, which was based on the English version of the Bible produced by Tyndale (1525). This English version without the doxology of the Our Father became accepted through the English speaking world.

Later, the Catholic Church made slight modifications in the English: "who art" replaced "which art" and  "on earth" replaced "in earth". During the reign of Elizabeth I, the Lord's Prayer was changed to include the doxology.  In this case we see that the Catholic Church has been faithful to the Gospel text of the Our Father. The doxology is still a beautiful prayer but one added by Tradition, not by Sacred Scripture.

Attending Mass can help non-Catholics to see the place of Mary and the other Saints in our worship and theology. The way we pray reflects the way we believe. Our prayers are focused on adoring the Most Blessed Trinity and encountering Jesus. Our Mass shows that our treasure is Jesus and our focus is on the Kingdom of God already present on earth and, after this life, Heaven. For many people, coming to Mass was their turning point. There they came to appreciate and love the Catholic Faith.

Source: Catholic Contact