Berachos (11b) I form the light, and create darkness; I make peace, and create evil; I the Lord do all these things.
Chagiga (015A) Acher became a heretic. Of him Scripture says: Suffer not thy mouth to bring thy flesh into guilt. What does it refer to? — He saw that permission was granted to Metatron to sit and write down the merits of Israel. Said he: It is taught as a tradition that on high there is no sitting and no emulation, and no back, and no weariness. Perhaps, — God forfend! — there are two divinities! Thereupon they led Metatron forth, and punished him with sixty fiery lashes, saying to him: Why didst thou not rise before him when thou didst see him? Permission was then given to him to strike out the merits of Aher. A Bas Kol went forth and said: Return, ye backsliding children — except Acher.
Eicha (03:38) Do not both evil and good come out of the mouth of the most High?
Moreh Nevuchim (03:010) I form the light and create darkness: I make peace, and create evil for darkness and evil are non-existing things. Consider that the prophet does not say, I make darkness, I make evil, because darkness and evil are not things in positive existence to which the verb “to make” would apply; the verb bara “he created” is used, because in Hebrew this verb is applied to non-existing things e.g., “In the beginning God created”, etc.; here the creation took place from nothing. Only in this sense can non-existence be said to be produced by a certain action of an agent. …It is now clear that according to an these different views the action of an agent cannot be directly connected with a thing that does not exist: only indirectly is non-existence described as the result of the action of an agent, whilst in a direct manner an action can only influence a thing really in existence; accordingly, whoever the agent may be, he can only act upon an existing thing.
Moreh Nevuchim (03:010) It must be admitted as a fact that it cannot be said of God that He directly creates evil, or He has the direct intention to produce evil: this is impossible. His works are all perfectly good. He only produces existence, and all existence is good: whilst evils are of a negative character, and cannot be acted upon. Evil can only he attributed to Him in the way we have mentioned. He creates evil only in so far as He produces the corporeal element such as it actually is: it is always connected with negatives, and is on that account the source of all destruction and all evil. Those beings that do not possess this corporeal element are not subject to destruction or evil: consequently the true work of God is all good, since it is existence. The book which enlightened the darkness of the world says therefore, “And God saw everything that He had made, and, behold, it was very good”. Even the existence of this corporeal element, low as it in reality is, because it is the source of death and all evils, is likewise good for the permanence of the Universe and the continuation of the order of things, so that one thing departs and the other succeeds. Rabbi Meir therefore explains the words “and behold it was very good” that even death was good in accordance with what we have observed in this chapter.
Moreh Nevuchim (03:10) All that the prophets and our Sages remarked about the perfect goodness of all the direct works of God. In Bereshis Rabba the same idea is expressed thus: “No evil comes down from above.”
Rabbeinu Bachya (Bereishis 04:02) and Kayin had become, The whole episode teaches that good and evil have the same root. The root by itself is totally good; after all when Adam was created he was totally good. Nonetheless we observe that from such a good “root,” two sons with totally different personalities emerged. Seeing that both wicked people and good people developed out of the same root is proof that there was only One Creator, that evil and good are not separate domains, that there are no two competing deities in this world, one promoting the source of all that is good and promoting it, and one which is the root of all that is bad and promoting same.
Ramchal (Derech HaShem 01:05.08) Created powers as the cause for the doing of evil: And you need to know that even though it is surely true that the cause of all good things in every place - meaning whether in the higher powers or in their outgrowths - is surely the emanation of His countenance and the cause of evil in every place is the hiding of His emanation; nevertheless only for the good is the Master described as the actual cause to its principles and its components. But as for the evil, we do not describe Him, as the actual cause. For the Holy One truly does not combine His name with evil. Rather it is the hiding of His light and the covering of His countenance that is considered its root. For that is its true cause; hence evil is actually the removal of good. However the Master who is omnipotent and who has no impediment to His will and no limit whatsoever to His ability - made a root and a specific source for the components of the contents of its existence, dedicated to this purpose of the expression of the components of evil, according to that which the Supreme Wisdom determined to be necessary for the desirable state for man and the world. And this is what is stated by the verse, "I form light and create darkness, I make weal and create evil." And the makeup of this root is the sum of the various powers. All of the matters of lacking and evil unfold from them in all of their aspects, whether regarding things that relate to the soul or that relate to the body in all of their components and sections.
Yishaya (45:07) I form the light, and create darkness; I make peace, and create evil; I the Lord do all these things.