Sunan an Nasai
2138
Sahih Isnaad+2

It was narrated that Abu Hurairah said:"The Messenger of Allah said: The month may be twenty-nine days or it may be thirty. When you see it, then stop fasting, and it is obscured from you (too cloudy), then complete the count

Sahih IsnaadAbu Ghuddah
Sahih IsnaadAl-Albani