Guide for the Perplexed, by Moses Maimonides, Friedländer tr. [1904], at sacred-texts.com
I NEED not explain what a dream is, but I will explain the meaning of the term mareh, "vision," which occurs in the passage: "In a vision (be-mareh) do I make myself known unto him" (Num. xii. 6). The term signifies that which is also called mareh ha-nebuah, "prophetic vision," yad ha-shem, "the hand of God," and maḥazeh, "a vision." It is something terrible and fearful which the prophet feels while awake, as is distinctly stated by
[paragraph continues] Daniel: "And I saw this great vision, and there remained no strength in me, for my comeliness was turned in me into corruption, and I retained no strength" (Dan, x. 8). He afterwards continues, "Thus was I in deep sleep on my face, and my face toward the ground" (ibid. ver. 9). But it was in a prophetic vision that the angel spoke to him and "set him upon his knees." Under such circumstances the senses cease to act, and the [Active Intellect] influences the rational faculties, and through them the imaginative faculties, which become perfect and active. Sometimes the prophecy begins with a prophetic vision, the prophet greatly trembles, and is much affected in consequence of the perfect action of the imaginative faculty: and after that the prophecy follows. This was the case with Abraham. The commencement of the prophecy is, "The word of the Lord came to Abraham in a vision" (Gen. xv. 1); after this, "a deep sleep fell upon Abraham"; and at last, "he said unto Abraham," etc. When prophets speak of the fact that they received a prophecy, they say that they received it from an angel, or from God; but even in the latter case it was likewise received through an angel. Our Sages, therefore, explain the words, "And the Lord said unto her" that He spake through an angel. You must know that whenever Scripture relates that the Lord or an angel spoke to a person, this took place in a dream or in a prophetic vision.
There are four different ways in which Scripture relates the fact that a divine communication was made to the prophet. (1) The prophet relates that he heard the words of an angel in a dream or vision; (2) He reports the words of the angel without mentioning that they were perceived in a dream or vision, assuming that it is well known that prophecy can only originate in one of the two ways, "In a vision I will make myself known unto him, in a dream I will speak unto him" (Num. xii. 6). (3) The prophet does not mention the angel at all; he says that God spoke to him, but he states that he received the message in a dream or a vision. (4) He introduces his prophecy by stating that God spoke to him, or told him to do a certain thing, or speak certain words, but he does not explain that he received the message in a dream or vision, because he assumes that it is well known, and has been established as a principle that no prophecy or revelation originates otherwise than in a dream or vision, and through an angel. Instances of the first form are the following:--"And the angel of the Lord said unto me in a dream, Jacob" (Gen. xxxi. 11); "And an angel said unto Israel in a vision of night" (ibid. xlvi. 2); "And an angel came to Balaam by night"; "And an angel said unto Balaam" (Num. xxii. 20-72). Instances of the second form are these: "And Elohim (an angel), said unto Jacob, Rise, go up to Bethel" (Gen. xxxv. 1); "And Elohim said unto him, Thy name is Jacob," etc. (ibid. xxxv. 10); "And an angel of the Lord called unto Abraham out of heaven the second time" (ibid. xxii. 15); "And Elohim said unto Noah" (ibid. vi. 13). The following is an instance of the third form: "The word of the Lord came unto Abraham in a vision" (ibid. xv. 1). Instances of the fourth form are: "And the Lord said unto Abraham" (ibid. xviii. 13); "And the Lord said unto Jacob, Return," etc. (ibid. xxxi. 3); "And the Lord said unto Joshua" (Josh. v. 9); "And the Lord said unto Gideon" (Judges vii. 2). Most of the prophets speak in a similar manner: "And the Lord said unto me" (Deut. ii. 2); "And the word of the Lord came unto me"
[paragraph continues] (Ezek. xxx. 1); "And the word of the Lord came" (2 Sam. xxiv. 11); "And behold, the word of the Lord came unto him" (1 Kings xix. 9); "And the word of the Lord came expressly" (Ezek. i. 3); "The beginning of the word of the Lord by Hosea" (Hos. i. 2); "The hand of the Lord was upon me" (Ezek. xxxvii. 1). There are a great many instances of this class. Every passage in Scripture introduced by any of these four forms is a prophecy proclaimed by a prophet; but the phrase, "And Elohim (an angel) came to a certain person in the dream of night," does not indicate a prophecy, and the person mentioned in that phrase is not a prophet; the phrase only informs us that the attention of the person was called by God to a certain thing, and at the same time that this happened at night. For just as God may cause a person to move in order to save or kill another person, so He may cause, according to His will, certain things to rise in man's mind in a dream by night. We have no doubt that the Syrian Laban was a perfectly wicked man, and an idolater; likewise Abimelech, though a good man among his people, is told by Abraham concerning his land [Gerar] and his kingdom, "Surely there is no fear of God in this place" (Gen. xx. 11). And yet concerning both of them, viz., Laban and Abimelech, it is said [that an angel appeared to them in a dream]. Comp. "And Elohim (an angel) came to Abimelech in a dream by night" (ibid. ver. 3); and also, "And Elohim came to the Syrian Laban in the dream of the night" (ibid. xxxi. 24). Note and consider the distinction between the phrases, "And Elohim came," and "Elohim said," between "in a dream by night," and "in a vision by night." In reference to Jacob it is said, "And an angel said to Israel in the visions by night" (Gen. xlvi. 2), but in reference to Laban and Abimelech, "And Elohim came," etc. Onkelos makes the distinction clear; he translates, in the last two instances, ata memar min kodam adonai, "a word came from the Lord," and not ve-itgeli, "and the Lord appeared." The phrase, "And the Lord said to a certain person," is employed even when this person was not really addressed by the Lord, and did not receive any prophecy, but was informed of a certain thing through a prophet. E.g., "And she went to inquire of the Lord" (Gen. xxv. 22); that is, according to the explanation of our Sages, she went to the college of Eber, and the latter gave her the answer; and this is expressed by the words, "And the Lord said unto her" (ibid. ver. 23). These words have also been explained thus, God spoke to her through an angel; and by "angel" Eber is meant here, for a prophet is sometimes called "angel," as will be explained; or the angel that appeared to Eber in this vision is referred to, or the object of the Midrash explanation is merely to express that wherever God is introduced as directly speaking to a person, i.e., to any of the ordinary prophets, He speaks through an angel, as has been set forth by us (chap. xxxiv.).