A Du'a which made the Angels confuse

إِنَّ عَبْدًا مِنْ عِبَادِ اللهِ قَالَ:يَا رَبِّ لَكَ الْحَمْدُ كَمَا يَنْبَغِي لِجَلَالِ وَجْهِكَ وَعَظِيمِ سُلْطَانِكَ. فَعَضَلَتْ بِالْمَلَكَيْنِ فَلَمْ يَدْرِيَا كَيْفَ يَكْتُبَانِهَا فَصَعِدَا إِلَى اللهِ فَقَالَا: يَا رَبَّنَا إِنَّ عَبْدًا قَدْ قَالَ مَقَالَةً لَا نَدْرِي كَيْفَ نَكْتُبُهَا، قَالَ اللهُ، وَهُوَ أَعْلَمُ بِمَا قَالَ عَبْدُهُ: مَاذَا قَالَ عَبْدِي؟ قَالَا: يَا رَبِّ إِنَّهُ قَالَ: لَكَ الْحَمْدُ يَا رَبِّ كَمَا يَنْبَغِي لِجَلَالِ وَجْهِكَ وَعَظِيمِ سُلْطَانِكَ. فَقَالَ اللهُ لَهُمَا: اكْتُبَاهَا كَمَا قَالَ عَبْدِي، حَتَّى يَلْقَانِي فَأَجْزِيهِ بِهَا.» 

A servant of Allah once said, `O Allah! Yours is the Hamd that is suitable for the grace of Your Face and the greatness of Your Supreme Authority.' The two angels were confused as to how to write these words. They ascended to Allah and said, `O our Lord! A servant has just uttered a statement and we are unsure how to record it for him.' Allah said while having more knowledge in what His servant has said, 'What did My servant say' They said, `He said, `O Allah! Yours is the Hamd that is suitable for the grace of Your Face and the greatness of Your Supreme Authority.' Allah said to them, `Write it as My servant has said it, until he meets Me and then I shall reward him for it.

Source: Tafsir Ibn Kathir: Tafsir of Soorah Al-Fatiha.