Sunan an-Nasai Book 12, Hadith 1131

أَخْبَرَنَا إِبْرَاهِيمُ بْنُ الْحَسَنِ الْمِصِّيصِيُّ الْمِقْسَمِيُّ، قَالَ حَدَّثَنَا حَجَّاجٌ، عَنِ ابْنِ جُرَيْجٍ، عَنْ عَطَاءٍ، قَالَ أَخْبَرَنِي ابْنُ أَبِي مُلَيْكَةَ، عَنْ عَائِشَةَ، قَالَتْ فَقَدْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم ذَاتَ لَيْلَةٍ فَظَنَنْتُ أَنَّهُ ذَهَبَ إِلَى بَعْضِ نِسَائِهِ فَتَحَسَّسْتُهُ فَإِذَا هُوَ رَاكِعٌ أَوْ سَاجِدٌ يَقُولُ ‏ "‏ سُبْحَانَكَ اللَّهُمَّ وَبِحَمْدِكَ لاَ إِلَهَ إِلاَّ أَنْتَ ‏"‏ ‏.‏ فَقُلْتُ بِأَبِي أَنْتَ وَأُمِّي إِنِّي لَفِي شَأْنٍ وَإِنَّكَ لَفِي آخَرَ ‏.‏

It was narrated that 'Aishah said:"I noticed that the Messenger of Allah (ﷺ) was missing one night, and I thought he had gone to one of his other wives. I tried to feel for him, and I found him bowing or prostrating and saying: 'SubhanakAllahumma wa bihamdika la ilaha ila ant (Glory and praise be to You, O Allah, there is none worthy of worship but You.)'" She said: "May my father and mother be ransomed for you. I thought you were doing one thing and you were doing something else altogether