Muawiya stood among the people at Dayr Mashal, which is at the gate of Hims, and said, "People, we have sighted the crescent on such-and-such a day, and I am beginning the fast early. Whoever wishes to do the same may do so."Malik bin Hubayra al-Sabai stood up and said to him, "Muawiya, is this something you heard from the Messenger of Allah ﷺ, or is it your own opinion?"Muawiya replied, "I heard the Messenger of Allah ﷺ say, 'Fast the month and its beginning.'"
حدثنا إبراهيم بن العلاء الزبيدي من كتابه حدثنا الوليد بن مسلم حدثنا عبد الله بن العلاء
قام معاوية في الناس بدير مسحل الذي على باب حمص فقال أيها الناس إنا قد رأينا الهلال يوم كذا وكذا وأنا متقدم فمن أحب أن يفعله فليفعله قال فقام إليه مالك بن هبيرة السبئي فقال يا معاوية أشيء سمعته من رسول الله ﷺ أم شيء من رأيك قال سمعت رسول الله ﷺ يقول صوموا الشهر وسره
No references are available.
[Its isnad is hasan]. Tabarani narrated it in Kabir, 19/384, no. 901, and in Musnad Shamiyin, 1/451, no. 795, through the hadith of Walid bin Muslim in this wording, and he explicitly stated that he heard it, with each narrator in the chain likewise stating that he heard it directly. Praise be to Allah.