An Arabi came to the Prophet ﷺ and said, "I have sighted the crescent moon."The Prophet ﷺ asked, "Do you bear witness that there is no god but Allah? Do you bear witness that Muhammad is the Messenger of Allah?"He replied, "Yes."The Prophet ﷺ said, "Bilal, announce to the people that they should fast tomorrow."Abu Kurayb narrated to us, Husayn al-Jufi narrated to us, from Zaidah, from Simak, a similar report with this chain of transmission.
حدثنا محمد بن إسمعيل حدثنا محمد بن الصباح حدثنا الوليد بن أبي ثور عن سماك عن عكرمة
جاء أعرابي إلى النبي ﷺ فقال إني رأيت الهلال قال أتشهد أن لا إله إلا الله أتشهد أن محمدا رسول الله قال نعم قال يا بلال أذن في الناس أن يصوموا غدا حدثنا أبو كريب حدثنا حسين الجعفي عن زائدة عن سماك نحوه بهذا الإسناد
[Its chain of transmission is daif]. Abu Dawud narrated it in the Book of Fasting, chapter on the testimony of a single witness regarding the sighting of the crescent of Ramadan, no. 2340, as did Ibn Majah, no. 1652, and Nasai, 4/131, 132, no. 2114, 2115, 131/4, from the hadith of Simak, with this wording. Ibn Khuzayma graded it sahih, no. 1923, 1924, as did Ibn Hibban (Al-Ihsan), 3437, and Hakim, 1/424. Simak's narration from Ikrima is daif according to the stronger view, but his narration from other than Ikrima is sahih.