Hadith #2321 (Sunan Abi Dawud)
Book: Fasting (Kitab Al-Siyam)
Narrator(s): Ahmed bin Manay' أحمد بن منيع, Amr bin al-Harith bin Abi Darar, ibn Mas'ud, Isa bin Dinar al-Khuza'i عيسى بن دينار الخزاعي أبو علي, Yahya bin Zakaria bin Abi Zaida يحيى بن زكريا بن أبي زائدة
Grade: Da'if

‘Umar b. ‘Abd al-‘Aziz wrote (a letter) to the people of Basrah: It has reached us from the Messenger of Allah (ﷺ), like the tradition narrated by Ibn ‘Umar from the Prophet (ﷺ). This version adds: The best calculation is that when we sight the moon of Sha’ban on such-and-such date, fasting will being on such-and-such dates, Allah willing, except they they sight the moon before that (date).

Source: https://parallelquran.com/hadith/sunan-abi-dawud-2321/