Heaping up empty phrases
Critics of Catholicism will often complain how we repeat prayers, saying that we are instructed not to do this.
7 And in praying do not heap up empty phrases as the Gentiles do; for they think that they will be heard for their many words.
8 Do not be like them, for your Father knows what you need before you ask him.
9 Pray then like this: Our Father who art in heaven, Hallowed be thy name.
10 Thy kingdom come. Thy will be done, On earth as it is in heaven.
11 Give us this day our daily bread;
12 And forgive us our debts, As we also have forgiven our debtors;
13 And lead us not into temptation, But deliver us from evil.
In the time when this was said by Jesus, there would have been no one who had never seen a pagan pray before but today most of us do not know what a praying Gentile looks like. Jesus clarifies what he means.
For pagans, gods do not care what goes on in the lives of the people beneath them. They are busy with their own concerns. Prayer is transactional. A lot of effort can go into just getting the god's attention to hear you out, whereas the True God already knows before you pray.
Immediately after specifying this detail, Jesus gives us our most repeated prayer, which we pray anyway even though God already knows about us before we offer it up. There is nothing empty about it.
Example of vain repitition: Calling Baal for hours
25 Then Eli'jah said to the prophets of Ba'al, "Choose for yourselves one bull and prepare it first, for you are many; and call on the name of your god, but put no fire to it."
26 And they took the bull which was given them, and they prepared it, and called on the name of Ba'al from morning until noon, saying, "O Ba'al, answer us!" But there was no voice, and no one answered. And they limped about the altar which they had made.
27 And at noon Eli'jah mocked them, saying, "Cry aloud, for he is a god; either he is musing, or he has gone aside, or he is on a journey, or perhaps he is asleep and must be awakened."
28 And they cried aloud, and cut themselves after their custom with swords and lances, until the blood gushed out upon them.
29 And as midday passed, they raved on until the time of the offering of the oblation, but there was no voice; no one answered, no one heeded.
Jesus prays a third time, saying the same thing again
44 So, leaving them again, he went away and prayed for the third time, saying the same words.
Collector kept beating breast and praying: Be merciful
13 But the tax collector, standing far off, would not even lift up his eyes to heaven, but beat his breast, saying, 'God, be merciful to me a sinner!'
Repeat day and night, "Holy, holy, holy is the Lord!"
8 And the four living creatures, each of them with six wings, are full of eyes all round and within, and day and night they never cease to sing, "Holy, holy, holy, is the Lord God Almighty, who was and is and is to come!"
Pray without ceasing
17 pray constantly,