The Messenger of Allah ﷺ said to me, "Shall I teach you a phrase from the treasures of Paradise?"I replied, "Yes, may my father and mother be your ransom."He said, "Say, 'There is no power and no strength except by Allah.'"
حدثنا أحمد بن عبد الملك قال حدثنا زهير قال حدثنا أبو بلج يحيى بن أبي سليم عن عمرو بن ميمون أنه حدثه قال
قال لي رسول الله ﷺ ألا أعلمك كلمة من كنز الجنة قال قلت نعم فداك أبي وأمي قال قل لا حول ولا قوة إلا بالله
Its chain of transmission is sahih. Bukhari related it, 8/156, in the Chapter on Divine Decree, "There is no power and no strength except by Allah," see also Fath al-Bari 11/500, no. 6610, and Tirmidhi, 5/457, no. 3374, in the Chapter on Supplication, Chapter on What Has Been Related Concerning the Merit of Supplication, chapter 3, and he graded it hasan.