Rambam on Divine Attributes in Prayer: The Limits of Human Power

One should also not add to the enumeration of Hashem’s attributes in the Shemoneh Esreh and say: ha’el ha’gadol ha’gibor v’ha’nora he’chazak v’ha’amitz v’ha’izuz, the great, mighty and awesome God, strong, brave and powerful. It is beyond human ability to fully praise God, except to say what Moshe said. (Tefillah 9:7)

This Rambam follows the Gemara:
A certain [reader] went down in the presence of R. Hanina and said, O God, the great, mighty, terrible, majestic, powerful, awful, strong, fearless, sure and honored. He waited till he had finished, and when he had finished he said to him, Have you concluded all the praise of your Master? Why do we want all this? Even with these three that we do say, had not Moses our Master mentioned them in the Law (Devarim 10:17) and had not the Men of the Great Synagogue come and inserted them in the Tefillah, we should not have been able to mention them, and you say all these and still go on! It is as if an earthly king had a million denarii of gold, and someone praised him as possessing silver ones. Would it not be an insult to him? (Berakhos 33b)

The Rambam explains this mashal in Moreh Nevukhim:
Consider, first, how repulsive and annoying the accumulation of all these positive attributes was to him; next, how he showed that, if we had only to follow our reason, we should never' have composed these prayers, and we should not have uttered any of them. It has, however, become necessary to address men in words that should leave some idea in their minds, and, in accordance with the saying of our Sages," The Torah speaks in the language of men," the Creator has been described to us in terms of our own perfections; but we should not on that account have uttered any other than the three above-mentioned attributes, and we should not have used them as names of God except when meeting with them in reading the Law. Subsequently, the men of the Great Synagogue, who were prophets, introduced these expressions also into the prayer, but we should not on that account use [in our prayers] any other attributes of God. The principal lesson to be derived from this passage is that there are two reasons for our employing those phrases in our prayers : first, they occur in the Pentateuch; secondly, the Prophets introduced them into the prayer. Were it not for the first reason, we should never have uttered them; and were it not for the second reason, we should not have copied them from the Pentateuch to recite them in our prayers: how then could we approve of the use of those numerous attributes! You also learn from this that we ought not to mention and employ ill our prayers all the attributes we find applied to God in the books of the Prophetq: for he does not say," Were it not that Moses, our Teacher, said them, we should not have been able to use them": but he adds another condition-" and had not the men of the Great Synagogue come forward and established their use in the prayer," because only for that reason are we allowed to use them in our prayers. We cannot approve of what those foolish persons do who are extravagant in praise, fluent and prolix in the prayers they compose, and in the hymns they make in the desire to approach the Creator. They describe God in attributes which would be an offence if applied to a human being; for those persons have no knowledge of these great and important principles, which are not accessible to the ordinary intelligence of man. Treating the Creator as a familiar object, they describe Him and speak of Him in any expressions they think proper; they eloquently continue to praise Him in that manner, and believe that they can thereby influence Him and produce an effect on Him. If they find some phrase suited to their object in the words of the Prophets they are still more inclined to consider that they are free to make use of such texts-which should at least be explained-to employ them in their literal sense, to derive new expressions from them, to form from them numerous variations, and to found whole compositions on them. This license is frequently met with in the compositions of the singers, preachers, and others who imagine themselves to be able to compose a poem. Such authors write things which partly are real heresy, partly contain such folly and absurdity that they naturally cause those who hear them to laugh, but also to feel grieved at the thought that such things can be uttered in reference to God. Were it not that 1 pitied the authors for their defects. And did not wish to injure them, I should have cited some passages to show you their mistakes; besides, the fault of their compositions is obvious to all intelligent persons. You must consider it, and think thus : If slander and libel is a great sin, how much greater is the sin of those who speak with looseness of tongue in reference to God, and describe Him by attributes which are far below Him; and I declare that they not only commit an ordinary sin, but unconsciously at least incur the guilt of profanity and blasphemy. This applies both to the multitude that listens to such prayers, and to the foolish man that recites them. Men, however, who understand the fault of such compositions, and, nevertheless, recite them, may be classed, according to my opinion, among those to whom the following words are applied:" And the children of Israel used words that were not right against the Lord their God" (2 Kings xvii. 9): and" utter error against the Lord" (Isa. =ii. 6). If you are of those who regard the honour of their Creator, do not listen in any way to them, much less utter what they say, and still less compose such prayers. knowing how great is the offence of one who hurls aspersions against the Supreme Being. There is no necessity at all for you to use positive attributes of God with the view of magnifying Him in your thoughts, or to go beyond the limits which the men of the Great Synagogue have introduced in the prayers and in the blessings, for this is sufficient for all purposes, and even more than Sufficient, as Rabbi Haninah said. Other attributes, such as occur in the books of the Prophets, may be uttered when we meet with them in reading those books; but we must bear in mind what has already been explained, that they are
either attributes of God's actions, or expressions implying the negation of the opposite. This likewise should not be divulged to the multitude; but a reflection of this kind is fitted for the few only who believe that the glorification of God does not consist in uttering that which is not to be uttered, but in reflecting on that on which man should reflect.

We Will now conclude our exposition of the wise words of R. Haninah. He does not employ any such simile as:" A king who possesses millions of gold denarii, and is praised as having hundreds" : for this would imply that God's perfections, although more perfect than those ascribed to man are still of the same kind: but this is not the case, as has been proved. The excellence of the simile consists in the words: who possesses golden denarii, and is praised as having silver denarii" this implies that these attributes, though perfections as regards ourselves, are not such as regards God; in reference to Him they would all be defects, as is distinctly suggested in the remark," Is this not an offence to Him ?" '
(Moreh I,59)

I always suspected that there is also anti-Islamic polemic here because the Muslims list a hundred attributes of God.