Abu Ala bin Shikhir reported,

I was with Mutarrif in the camel market when an Arabi came to him carrying a piece of leather, or a satchel. He said, "Who can read? Is there anyone among you who can read?"I said, "Yes."So I took it, and there was written, "In the name of Allah, the Most Gracious, the Most Merciful. From Muhammad, the Messenger of Allah, to the Banu Zuhayr bin Uqaysh, a clan of Ukl. If they testify that there is no god but Allah and that Muhammad is the Messenger of Allah, separate themselves from the polytheists, and acknowledge the fifth due from their war spoils, along with the Prophet's ﷺ share and his chosen portion, then they shall have the protection of Allah and His Messenger."Some of the people said to him, "Have you heard anything from the Messenger of Allah ﷺ that you can relate to us?"He replied, "Yes."They said, "Then narrate to us, may Allah have mercy on you."He said, "I heard him say, 'Whoever wishes to remove much of the rancor in his chest, let him fast the month of patience and three days of every month.'"Some of the people, or one of them, said to him, "Did you yourself hear this from the Messenger of Allah ﷺ?"He replied, "Do I see you accusing me of lying about the Messenger of Allah ﷺ?" Ismail once said, "Do I see you suspecting me? By Allah, I will not narrate a single hadith to you for the rest of the day." Then he left.

Azami 4453

Sahih

عن أبي العلاء بن الشخير، قال

كنت مع مطرف في سوق الإبل، فجاءه أعرابي معه قطعة أديم، أو جراب، فقال: من يقرأ أو فيكم من يقرأ؟ قلت: نعم، فأخذته فإذا فيه: بسم الله الرحمن الرحيم، من محمد رسول الله، لبني زهير بن أقيش- حي من عكل- أنهم إن شهدوا أن لا إله إلا الله وأن محمدا رسول الله، وفارقوا المشركين، وأقروا بالخمس في غنائمهم، وسهم النبي ﷺ وصفيه، فإنهم آمنون بأمان الله ورسوله. فقال له بعض القوم: هل سمعت من رسول الله ﷺ شيئا تحدثناه؟ قال: نعم. قالوا: فحدثنا يرحمك الله، قال: سمعته يقول: من سره أن يذهب كثير من وحر صدره فليصم شهر الصبر، وثلاثة أيام من كل شهر. فقال له القوم أو بعضهم: أأنت سمعت هذا من رسول الله ﷺ؟ فقال: ألا أراكم تتهموني أن أكذب على رسول الله ﷺ؟ وقال إسماعيل مرة: تخافون. والله لا أحدثنكم حديثا سائر اليوم. ثم انطلق.

الأعظمي 4453صحيح
Contents
Reference
Commentary
Ayat
Collection
Jami al-Kamil
Book
Fasting
Chapter
Voluntary fasting and encouragement to do it
Section
Fasting three days of every month
Numbering
Jami al-Kamil 4453 (2nd edition)
Azami 4453