Scripture:
Mt. 6:7 "But when ye pray, use not vain repetitions, as the heathen do: for they think that they shall be heard for their much speaking." [KJV]
Did Jesus actually mean that someone praying to God could not repeat a prayer or even a phrase?
Jesus could not possibly mean that a person could not repeat a phrase in a prayer or repeat a whole prayer, because we can see from Scripture that His followers did just that.
2 Cor. 12:8 "2 Cor. 12:8 For this thing I besought the Lord thrice, that it might depart from me." [KJV]
From the above we see Paul repeating a prayer 3 times.
Jesus Himself repeats the "saying the same words".
Mt 26:42 "He went away again the second time, and prayed, saying, O my Father, if this cup may not pass away from me, except I drink it, thy will be done. 43 And he came and found them asleep again: for their eyes were heavy. 44 And he left them, and went away again, and prayed the third time, saying the same words." [KJV]
What was Jesus really saying when He admonished against the practice of "vain repetition"?
He is talking about what the Bible constantly talks about, that is, doing things from your 'heart'. It obviously doesn't matter how much a phrase or a prayer is repeated it is your heart that counts. If you pray from the heart [Rom. 2:29; 1 Sam. 16:7] and are seeking righteousness [Jam. 5:16], that is what counts.
He was also telling His followers that no one can force the Hand of God by the shear number of prayers.