Yes, consulting a horoscope is a sin. Consulting horoscopes is a form of divination, a practice condemned by the Bible. The future is not defined by the stars. To believe in the horoscope is to believe a lie.
What is the horoscope?
The horoscope is a set of predictions for the future based on the position of the stars. People are grouped into categories, called signs, according to the time of year they were born. People of the same sign receive the same forecast for the future.
See also: is it sin to sympathize?
Why is it wrong to believe in horoscopes?
The horoscope prediction does not come from God’s revelation. Only God knows the future but the horoscope says that he can predict the future without God ( Isaiah 44: 7-8 ).
In its most innocent form, the horoscope uses personality traits that we all have and vague things that happen to everyone to look like they are predicting the future. In its most dangerous form, a horoscope does the same but with the help of demons ( Acts 16:16 ). The horoscope cannot really predict the future.
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In the horoscope, completely different people, with different lives, receive the same forecast for the future just because they were born at the same time of the year. In addition, different horoscopes can give completely different predictions for the same sign. This is ridiculous. The horoscope has no basis.
Consulting the horoscope is a way to practice divination ( Deuteronomy 18: 10-12 ). In addition to being based on unfounded superstition, this is putting the horoscope in the place of God. Only God knows us completely and can give us guidance for the future. Our future is not tied to predictions based on the stars.
Want to know more about divination in the Bible? See here: what does the Bible say about witchcraft?