Philo Judaeus De Opificio Mundi 33

[33] And after the shining forth of that light, perceptible only to the intellect, which existed before the sun, then its adversary darkness yielded, as God put a wall between them and separated them, well knowing their opposite characters, and the enmity existing between their natures. In order, therefore, that they might not war against one another from being continually brought in contact, so that war would prevail instead of peace, God, turning want of order into order, did not only separate light and darkness, but did also place boundaries in the middle of the space between the two, by which he separated the extremities of each. For if they had approximated they must have produced confusion, preparing for the contest, for the supremacy, with great and unextinguishable rivalry, if boundaries established between them had not separated them and prevented them from clashing together,