The Prophet ﷺ said: If anyone acquires any knowledge of astrology, he acquires a branch of magic of which he gets more as long as he continues to do so.  

قَالَ رَسُولُ اللَّهِ ﷺ مَنِ اقْتَبَسَ عِلْمًا مِنَ النُّجُومِ اقْتَبَسَ شُعْبَةً مِنَ السِّحْرِ زَادَ مَا زَادَ  

The Messenger of Allah ﷺ led us in the morning prayer at al-Hudaibiyyah after rain which has fallen during the night, and when he finished, he turned to the people and said: Do you know what your Lord has said ? They said: Allah and His Apostle know best. He said: This morning there were among mt servants one who believes in me and one who disbelieves. The one who said: "We have been given rain by Allah's grace and mercy" is the one who believes in me and disbelieves in the star ; but the one who said: "We have been given rain by such and such a rain star," is the one who disbelieves in me and believes in the star.  

أَنَّهُ قَالَ صَلَّى لَنَا رَسُولُ اللَّهِ ﷺ صَلاَةَ الصُّبْحِ بِالْحُدَيْبِيَةِ فِي إِثْرِ سَمَاءٍ كَانَتْ مِنَ اللَّيْلِ فَلَمَّا انْصَرَفَ أَقْبَلَ عَلَى النَّاسِ فَقَالَ هَلْ تَدْرُونَ مَاذَا قَالَ رَبُّكُمْ قَالُوا اللَّهُ وَرَسُولُهُ أَعْلَمُ قَالَ قَالَ أَصْبَحَ مِنْ عِبَادِي مُؤْمِنٌ بِي وَكَافِرٌ فَأَمَّا مَنْ قَالَ مُطِرْنَا بِفَضْلِ اللَّهِ وَبِرَحْمَتِهِ فَذَلِكَ مُؤْمِنٌ بِي كَافِرٌ بِالْكَوْكَبِ وَأَمَّا مَنْ قَالَ مُطِرْنَا بِنَوْءِ كَذَا وَكَذَا فَذَلِكَ كَافِرٌ بِي مُؤْمِنٌ بِالْكَوْكَبِ