John Chrysostom
Catena Aurea · Matthäusevangelium 6
But when ye pray, use not vain repetitions, as the heathen do: for they think that they shall be heard for their much speaking. Be ye not therefore like unto them: for your Father knoweth what things ye have need of, before ye ask Him.
Hereby He dissuades from empty speaking in prayer; as, for example, when we ask of God things improper, as dominions, fame, overcoming of our enemies, or abundance of wealth. He commands then that our prayers should not be long; long, that is, not in time, but in multitude of words. For it is right that those who ask should persevere in their asking; being instant in prayer, as the Apostle instructs; but does not thereby enjoin us to compose a prayer of ten thousand verses, and speak it all; which He secretly hints at, when He says, Do not ye use many words.