Q. 1. Why is it that in the Catholic liturgy and in many prayers, it ends by saying "In Jesus' Name, I pray"?
A. 1. When you pray in Jesus' Name, it means the same as praying according to the Divine Will of God. When one prays to God the Father in Jesus' Name, he recalls the intimate relationship between the Father and the Son, responding to Jesus' invitation to enter into it to become one with Jesus as Jesus and the Father are One.
Numerous Bible verses command us to pray in the Name of Jesus, namely:
"And this is the confidence which we have in him, that if we ask anything according to his will he hears us. 15 And if we know that he hears us in whatever we ask, we know that we have obtained the requests made of him." [1 Jn. 5:14-15; RSVCE: Revised Standard Version Catholic Edition]
"Believe me that I am in the Father and the Father in me; or else believe me for the sake of the works themselves. 'Truly, truly, I say to you, he who believes in me will also do the works that I do; and greater works than these will he do, because I go to the Father. Whatever you ask in my name, I will do it, that the Father may be glorified in the Son.'" [Jn. 14:11-13]
"You did not choose me, but I chose you and appointed you that you should go and bear fruit and that your fruit should abide; so that whatever you ask the Father in my name, he may give it to you." [Jn. 15:16]