Many unsaved people practice astrology (i.e., horoscopes) and other unscriptural use of the signs in the heavens. Believers should reject these practices.
When men choose to reject the truth, God tends to withhold further truth from them. The result is spiritual and intellectual darkness.
Most people view sin as a private or earthy matter. Yet, every sin is against the Lord. In truth, men can sin against the Father, the Son, and the Spirit.
