Sayyidah Aishah Siddiqah (may Allah be pleased with her) narrates: Once she found the Prophet (peace and blessings be upon him) missing from his bed. (In the dark) she felt for the Prophet (peace and blessings be upon him) with her hand, and her hand touched the body of the Prophet (peace and blessings be upon him). At that time the Prophet (peace and blessings be upon him) was in prostration and was reciting:
'Rabbi a'ti nafsi taqwaha, zakkiha anta khayru man zakkaha, anta waliyyuha wa mawlaha'
"O Allah, grant my soul its piety and purify it; only You can purify it; You are its Guardian and its Master."
Ahmad recorded it, and its narrators are the narrators of the Sahih, except for Salih bin Sa'id, the narrator who transmits it from Sayyidah Aishah (may Allah be pleased with her), and he is thiqah (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الأذكار / 16968