The section of Matthew you are referencing is Matthew 6:7, I assume, which reads "When you are praying, do not heap up empty phrases as the Gentiles do; for they think that they will be heard because of their many words." (NRSV) I thought of writing my own reply, but soon realized I could do no better than Ulrich Luz does in his commentary on Matthew 1-7. Here, at length, is his analysis of the verse, with apologies for the Greek characters which I don't think I can type in reddit:

The meaning and the etymology of the quite rare word battalogevw are matters of dispute. It is most probably related to the substantives bavttalo~ or bavtto~ (stutterer) or the verb battarivzw (to stutter). It probably means the repetition of meaningless syllables. The content of the word is repeated in the expression “many words” (polulogiva). The prohibition is probably thinking of Gentile prayers that by accumulating epithets for God or also words of magic give the impression of babbling. As a positive contrast to such babbling Matthew emphasizes the Lord’s Prayer as a short prayer. This meaning, which would appear to make sense, was obscured in the tradition of Greek interpretation. There one interpreted battalogevw in the sense of fluariva (meaningless gossip) and applied the warning not to the length but to the content of the prayer. The text thus forbids asking for unseemly things, that is, unspiritual, lowly, earthly things, the things below for which one is not to pray. Then the Lord’s Prayer— even in the interpretation of the petition for bread— becomes an instruction of how one is to ask for heavenly things. The Latin interpretive tradition never accepted this exegesis, and rightly so, although its right interpretation caused some difficulties in view of the verbosity of ecclesiastical prayers. If this logion were only an admonition to pray short prayers, it would agree with many Jewish texts and even with many Hellenistic statements. However, it has a special aim. The subordinate statement of v. 7b already shows that long winded prayers are not criticized as such; they are criticized as a means of gaining a hearing with God. The parallel rationale in v. 8b repeats this scope: the central theme of this logion is not a prayer’s length but whether it is heard. Long prayers are not necessary, because God knows what people need before they even ask. The issue is not simply preventing manipulation, nor is it that God knows everything anyway and that prayer is no longer necessary at all; it is that God in his love is with people before they pray and thus relieves them of the need to pray long-winded prayers. This text belongs with others that speak of the absolute certainty that prayer is heard and of God’s nearness to people (cf. Matt 7:7-11; Luke 11:5-8; 18:2-7; and the way God is addressed in the Lord’s Prayer). This absolute certainty that prayer is heard is characteristic of Jesus. He probably linked up with the Jewish expectation that in the new world God answers people before they call on him. Bringing this hope into the present is part of the dawning of the kingdom of God in the here-and-now. Of course, he does not intend to make prayer superfluous; he wants to encourage prayer. The church’s traditional interpretation, which repeatedly had to wrestle with the question whether prayer is still necessary at all, has understood this well, unlike modern Enlightenment. Cocceius states it pointedly: “Our prayer is not the reason for God’s gifts that we receive but more a sign that God has prepared his gifts for us.” That is, the prayer commanded by God is based on the promise that it will be answered. (Luz, Matthew 1-7, 305-6)

For further reading, see Eduard Norden, Agnostos Theos: Untersuchungen zur Formengeschichte religiöser Rede (1913; reprinted Darmstadt: Wissenschaftliche Buchgesellschaft, 1956) 146–49. As Luz comments "The hymn to Isis in Apuleius Met. 11.2 gives an example of the accumulation of epithets; cf. in addition Acts 19:34 (two hours); Virgil Aen. 4.510 (300 gods). Sarcastically Terentius, 5.1.6-7 (“idem dictum est centies”); Lucian Timon 11; Martial, 7.60.3." (Luz, Matthew 1-7, 305 n.5)

Sources: Luz, Ulrich. Matthew 1-7, trans Helmut Koester. Minneapolis: Augsburg Fortress Press, 2007.