The Bible never contradicts itself.
Actually the Bible doesn’t say not to repeat prayers. Here is what it says:
Matthew 6 [7] (http://www.drbo.org/x/d?b=drb&bk=47&ch=6&l=7#x) And when you are praying, speak not much, as the heathens. For they think that in their much speaking they may be heard.
Remember that here the heathens are wrongly thinking that by speaking out, they will be heard (obviously by their false Gods who cannot even hear). He advises us to go into our room and pray in secret. Nothing there about repetative prayer. In fact He goes on to teach them the Our Father, which He meant to be prayed often, obviously.
Luke 18: [1] (http://www.drbo.org/x/d?b=drb&bk=49&ch=18&l=1#x) And he spoke also a parable to them, that we ought always to pray, and not to faint, [2] (http://www.drbo.org/x/d?b=drb&bk=49&ch=18&l=2#x)Saying: There was a judge in a certain city, who feared not God, nor regarded man. [3] (http://www.drbo.org/x/d?b=drb&bk=49&ch=18&l=3#x) And there was a certain widow in that city, and she came to him, saying: Avenge (do me justice) me of my adversary. [4] (http://www.drbo.org/x/d?b=drb&bk=49&ch=18&l=4#x) And he would not for a long time. But afterwards he said within himself: Although I fear not God, nor regard man, [5] (http://www.drbo.org/x/d?b=drb&bk=49&ch=18&l=5#x) Yet because this widow is troublesome to me, I will avenge her, lest continually coming she weary me.[6] (http://www.drbo.org/x/d?b=drb&bk=49&ch=18&l=6#x) And the Lord said: Hear what the unjust judge saith. [7] (http://www.drbo.org/x/d?b=drb&bk=49&ch=18&l=7#x) And will not God revenge his elect who cry to him day and night: and will he have patience in their regard? [8] (http://www.drbo.org/x/d?b=drb&bk=49&ch=18&l=8#x) I say to you, that he will quickly revenge them. But yet the Son of man, when he cometh, shall he find, think you, faith on earth?
The story of the wicked judge shows how persistence pays. Even such a wicked person as the judge gave in because he was fed up with the woman. (The squeaky wheel gets the oil!) The message is how much more likely it is that your needs will be filled (though not necessarily your “wants”) by a just, generous and loving Father.
God never gets fed up of our prayers. He just can’t have enough of them. Or rather I should say it is impossible to pray too much.
A centurion, Cornelius, is described in the Acts of the Apostles, Chapter 10 [2] (http://www.drbo.org/x/d?b=drb&bk=51&ch=10&l=2#x) as
A religious man, and fearing God with all his house, giving much alms to the people, and always praying to God.
This gentile was not even baptised, and yet through his prayers, God gave him, and all his household, his reward and filled his needs with the grace of the Holy Spirit and of Baptism.
Theres also this:
1 Par (1 Chronicles) 21:1-- And satan rose up against Israel and moved David to number Israel
2 Kings (2 Samuel) 24:1-- And the anger of the Lord was again kindled against Israel, and stirred up David among them saying "Go and number Israel and Juda."
I'm pretty sure only the original manuscrtpts are considered infallible or inerrant. There are too many contradictions found in the Bible, especially in terms of verses that contain numbers.
And as for Matt. 6:7, I was thinking perhaps he meant not to speak much or babble when praying thinking that by doing so, others will hear and praise you for your piety.