Matthew Poole and continuators on Matthew 6:8

8 Be not ye therefore like unto them, for your Father knows what things ye have need of, before ye ask him.

It appeareth from hence, and from what followeth also, that the Praying here spoken of, is Vocal Prayer, not the meer Homage which the Heart payeth to God, by a Recognition of him as the Fountain of all Good, and our secret Desires that God would supply our Wants, but the Expression of those Desires by the words of our Mouths, which is that Duty which the Scripture generally calleth Prayer, and is most certainly a Duty incumbent on every Person. Nor are Repetitions of the same Requests in Prayer, or much speaking (that is Praying to some length of time) here absolutly forbidden: Our Saviour before his Passion prayed thrice, for the same thing within a short Compass of time (tho he did not use the same words) and Luk. 6.12. he continued all Night in Prayer to God. But that which is here forbidden, is an Opinion of being heard, for over long Prayers, and using Vain Repetitions as the Priests of Baal, continued from Morning to Night crying, O Baal hear us! O Baal hear us, (as if their God had been asleep, or gone a Journey, as the Prophet mocketh them, 1 Kin. 18.27, 28) Repetitions are then Vain, when they are affected and flow from some irreverent Thoughts we have of God: Not when they are as it were forced from the Heat and Intension of our Affections. The like is to be said of much speaking in Prayer. Long Prayers are not to be Condemned, but the Affectation of them is, and Long Prayers upon Pretences, and Designs are: But when the mind is attent, and the Affections servent, length of Prayer is no Fault, especially upon solemn Occasions, when we come not to ask a particular Mercy at the hand of God, nor for a particular Person, or Family. But Repetitions after the manner of Heathens, are Condemned as proceeding from irreverent Thoughts of God, as if he did not know what things we have need of, or were like a Man to be prevail'd upon by a multitude of Words.