Celsus appears to me to have heard that there are treatises in existence which contain allegorical explanations of the law of Moses. These however, he could not have read; for if he had he would not have said: “The allegorical explanations, however, which have been devised are much more shameful and absurd than the fables themselves, inasmuch as they endeavour to unite with marvellous and altogether insensate folly things which cannot at all be made to harmonize.” He seems to refer in these words to the works of Philo, or to those of still older writers, such as Aristobulus.
But I conjecture that Celsus has not read their books, since it appears to me that in many passages they have so successfully hit the meaning (of the sacred writers), that even Grecian philosophers would have been captivated by their explanations; for in their writings we find not only a polished style, but exquisite thoughts and doctrines, and a rational use of what Celsus imagines to be fables in the sacred writings. I know, moreover, that Numenius the Pythagorean— a surpassingly excellent expounder of Plato, and who held a foremost place as a teacher of the doctrines of Pythagoras— in many of his works quotes from the writings of Moses and the prophets, and applies to the passages in question a not improbable allegorical meaning, as in his work called Epops, and in those which treat of “Numbers” and of “Place.”
And in the third book of his dissertation on The Good, he quotes also a narrative regarding Jesus— without, however, mentioning His name— and gives it an allegorical signification, whether successfully or the reverse I may state on another occasion. He relates also the account respecting Moses, and Jannes, and Jambres. But we are not elated on account of this instance, though we express our approval of Numenius, rather than of Celsus and other Greeks, because he was willing to investigate our histories from a desire to acquire knowledge, and was (duly) affected by them as narratives which were to be allegorically understood, and which did not belong to the category of foolish compositions.
Source: Against Celsus (New Advent)