Ibn ʿAbbās—may Allah be pleased with him—reported that the Messenger of Allah, peace and blessings be upon him, said, “Whoever acquires a branch of astrology has thereby acquired a branch of sorcery; the more he increases, the more he increases.” (1) Reported by Abū Dāwūd with a sound chain of transmission.

Man iqtabasa: whoever learns.
Shuʿbah: a group or a portion.
A branch of sorcery: sorcery whose prohibition is well established.
Zāda mā zād: that is, each time he adds to his knowledge of the stars, his burden of sin grows in proportion to that of the sorcerer, or he has accrued additional branches of sorcery commensurate with the increase in his astrological learning.

Overall meaning of the ḥadīth: In this narration the Prophet—peace and blessings be upon him—issues, by way of report, a prohibition and a warning: whoever learns anything of astrology has learned something of the forbidden art of sorcery, and the more he delves into astrology the deeper he delves into sorcery. The reason is that astrology presumes authority over the unseen; the astrologer seeks to uncover future events that belong exclusively to the knowledge Allah has reserved for Himself.

Connection of the ḥadīth to the chapter: The Prophet—peace and blessings be upon him—makes it clear that astrology is one form of sorcery.