I came to the Messenger of Allah ﷺ and said, "Instruct me with something I can take from you."He replied, "Hold fast to fasting, for there is nothing like it."
أخبرنا عمرو بن علي عن عبد الرحمن قال حدثنا مهدي بن ميمون قال أخبرني محمد بن عبد الله بن أبي يعقوب قال أخبرني رجاء بن حيوة
أتيت رسول الله ﷺ فقلت مرني بأمر آخذه عنك قال عليك بالصوم فإنه لا مثل له
[Its isnad is sahih]. Ahmad narrated it, 5/249, 255, 258, from the hadith of Mahdi through him. It is also in Kubra, hadith 2530. Ibn Hibban graded it sahih, hadith 929, as did Ibn Hajar in Fath al-Bari, 4/104.