I don't know about this but Mohammad did say (in one of his sayings) that true dreams (i.e. dreams that will come true or dreams that are actually command from God) is one of 46 "attributes" of a prophet.
He certainly did not if this comes from the hadiths, which it does:
(29:5622) Abu Huraira reported: I love to see fetters but I hate necklaces (in a dream), for fetters signifies one's steadfastness in religion, and he also reported Allah's Messenger (may peace be upon him) as saying: The vision of a believer is forty-sixth part of Prophecy.
The hadiths are wicked fabrications replete with all manner of vulgarities to desecrate the Prophet, and yet they form a bedrock of the Sunni sect of Islam, and the Shi'ites also have their own hadith compilations. It is no coincidence that the horrendous deeds carried out in the world can always be traced back to members of one of these two sects. This is despite the fact that Quran states unequivocally that there are to be no sects, and that nothing is to be followed other than the example of the Prophet, via the Quran.
We can only know what the Seal of the Prophets said, peace be upon him, via the Quran. If it doesn't come from the Quran, it was not uttered by Muhammad. In many places, we know the sayings of Muhammad in that he receives direct guidance upon what to say when he is met with certain inquiries.
For the truth about the hadiths, the so called 'sayings of the prophet', I'll pass you over to Mohammed Abdul Malek, who can explain things a lot better than I can:
http://members.aol.com/MAmalek2/qbook10.htm
http://members.aol.com/MAmalek2/qbook.htm
The Quran forbids the practice of sortilege, such as divination by Tarot cards, runes or any other method of casting fortunes at random, as expressed in this verse:
(5:90) O ye who believe! Intoxicants and games of chance and idols and divining arrows are only an infamy of Satan's handiwork. Leave it aside in order that ye may succeed.
The reference to 'divining arrows' refers to methods of sortilege or cleromancy. Astrology however, is not casting fortunes at random, and this is not forbidden in the Quran, but in fact, the Quran implies that perhaps we can and should make use of such knowledge:
(3:109) Behold! In the creation of the heavens and the earth, and the alteration of Night and Day - there are indeed signs for men of understanding.
(6:96-98 ) He it is that cleaves the daybreak: He makes the night for rest and tranquillity, and the sun and moon for the reckoning. Such is the judgement and ordering of, the Exalted in Power, the Omniscient. It is he who makes the stars for you, that you may guide yourselves, with their help, through the dark spaces of land and sea: We detail Our signs for people who know. It is He who has produced you from a single person: here is a place of sojourn and a place of departure. We detail our signs for people who understand.
(10:05) It is He who made the sun to be a shining glory and the moon to be a light; and measured out stages for her; that you might know the number of years and the count. Nowise did God create this but in truth and righteousness. He does explain his signs in detail for those who understand. Surely in the alteration of the Night and the Day, and in all that God has created, in the heavens and the earth, are Signs for those that fear Him.
(13:02) God is He who raised the heavens without any pillars that you can see; is firmly established on the Throne; he has subjected the sun and moon! Each one runs for a term appointed. He does regulate all affairs, explaining the Signs in detail, that you may believe in certainty in the meeting with your Lord.
(14:33) And He has made subject to you the sun and the moon, both diligently pursuing their courses. And the Night and the Day has He made subject to you. And He gives you all that you ask for. But if you count the favours of God, never will you be able to number them. Surely, man is given up to injustice and ingratitude.
(16:12) He has made subject to you the Night and the Day; the Sun and the Moon, and the Stars are in subjection by His Command: surely in this are signs for men who are wise.
(21:32) And we have made the heavens as a canopy well guarded: yet do they turn away from the signs which these things point to! It is He who created the Night and the Day, and the sun and the moon, all swim along, each in it?s rounded course.
(41:37) Among His signs are the Night and the Day, and the Sun and the Moon, Prostrate not before the Sun and the Moon, but worship God, Who created them, if it is Him you wish to serve.
(45:13) And He has subjected to you, as from Him, all that is in the heavens and on earth: behold, in that are Signs indeed for those who reflect.
The Quran also provides this disclaimer:
(17:36) And pursue not that of which you have no knowledge; for every act of hearing, or of seeing or of the heart will be enquired into.
According to another translation:
(17:36) You shall not accept any information, unless you verify it for yourself. I have given you the hearing, the eyesight, and the brain, and you are responsible for using them.