Mishkat al-Masabih
Abu Dharr said that God’s messenger was asked what words were most excellent and replied, “What God has chosen for His angles: Glory be to God and I begin with praise of Him.” Muslim transmitted it.
وَعَنْ أَبِي ذَرٍّ قَالَ: سُئِلَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أَيُّ الْكَلَامِ أَفْضَلُ؟ قَالَ: " مَا اصْطَفَى اللَّهُ لِمَلَائِكَتِهِ: سُبْحَانَ اللَّهِ وَبِحَمْدِهِ ". رَوَاهُ مُسلم
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