TABARANI 11757:
from Ibn ʿAbbās —
[Machine] The Messenger of Allah ﷺ said, "Do not begin the month (of Ramadan) until you see it (the crescent moon), and end the month when you see it (the crescent moon). If it is obscured from you, then complete the count (of days)."
الطبراني ١١٧٥٧:
عن ابن عباس —
قَالَ رَسُولُ اللهِ ﷺ «لَا تَسْتَقْبِلُوا الشَّهْرَ صُومُوا لِرُؤْيَتِهِ وَأَفْطِرُوا لِرُؤْيَتِهِ فَإِنْ حَالَتْ دُونَهُ غَيَايَةٌ فَأَكْمِلُوا الْعِدَّةَ»