Mishkat al-Masabih 9 Supplications كتاب الدعوات 74

وَعَنْ أَبِي ذَرٍّ قَالَ: سُئِلَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أَيُّ الْكَلَامِ أَفْضَلُ؟ قَالَ: ” مَا اصْطَفَى اللَّهُ لِمَلَائِكَتِهِ: سُبْحَانَ اللَّهِ وَبِحَمْدِهِ ” . رَوَاهُ مُسلم

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.