Mishkat al-Masabih
Ibn Umar told that he heard God’s Messenger say, “He who swears by anyone but God is a polytheist.” Tirmidhi transmitted it.
وَعَنِ ابْنِ عُمَرَ رَضِيَ اللَّهُ عَنْهُمَا قَالَ: سَمِعْتُ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَقُولُ: «مَنْ حَلَفَ بِغَيْرِ اللَّهِ فَقَدْ أَشْرَكَ» . رَوَاهُ التِّرْمِذِيّ
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