In Islam, the clear guidance states that Allah is the only one authority who knows the unknown, the events of the future and possess the knowledge of Ghaib (the unseen). Therefore astrologers and fortune tellers try to practice this quality of God by foretelling the future events and predict future happenings in advance, which is totally haram according to Islam.
People buy books from thousands of astrologers to know about their future. Visiting an astrologer is also haram and reading the horoscope is also forbidden in Islam. If people had been given the power to predict the accurate future, then it would be easy to worship them. Since God does not reveal the exact knowledge of future to anyone, whoever seeks horoscope are committing a sin:
‘The Salaah (daily prayer) of whoever approaches a fortuneteller and asks him about anything will not be accepted for forty days and nights.’ [Saheeh Muslim vol.4,p. 1211, no 5440]
The simple hadith tells us all about the severe consequences of visiting a fortune teller and the punishment that is associated with it. No one knows the future besides Allah, Allah does not want to talk to or accept their prayers for 40 days and nights who ever commit this form of shirk, because Allaah clearly stated:
“And with Him are the keys of ghayb [all that is hidden], none knows them but He and He knows whatever there is in [or on) the earth and the sea; not a leaf falls, but the knows it. There is not a grain in the darkness of the earth nor anything fresh or day, but is written in a clear record.” [6:59]
“Say: None in the heavens and the earth knows the ghaby (unseen) except Allaah, nor can they perceive when they shall be resurrected.” [27:65]
The believer of astrologers and fortune tellers is a kafir, he falls directly into kufr (disbelief) as stated by the Prophet sallallaahu ‘alayhi wa sallam:
‘“Whoever approaches an oracle or fortune-teller and believes in what he says, has disbelieved in what was revealed to Muhammad.” [Reported by Abu Hurayrah and collected by Ahmad and Abu Daawood (Sunan Abu Dawud (English Trans.), vol. 3, p. 1095, no. 3895).]
The fortune tellers are doing their acts opposed to Tawheed concept. They are trying to interfere with God’s work in the lives of humans, therefore going and listening to them is strictly prohibited. They sometimes claim the wrong knowledge of one’s future to make huge money and deceive the innocent people with their astrology predictions. The lives of human beings are not written in stars, the lines in a palm are used to reveal the knowledge of the unseen. This is an insane attempt to escape the fate, it is not possible to stop anything bad from happening by going to the astrologer.
“Say (O Muhammad sallallaahu ‘alayhi wa Sallam): ‘ I possess no power over benefit or hurt to myself except as Allaah wills. If I had the knowledge of the ghayb (unseen), I should have secured for myself an abundance of wealth, and no evil should have touched me. I am but a warner, and a bringer of glad tidings unto people who believe.” [7:188]
Therefore true Muslims are strictly obliged to stay away from these people who use amulets, zodiac signs and stones to define their future and happiness.
Source: missionislam.com/knowledge/horoscope.html