Abdullah bin Umar reported,

I heard the Messenger of Allah ﷺ say, "When you see it, fast, and when you see it, break your fast. If it is obscured from you, then estimate it."

Muslim 2504

Sahih

حدثني حرملة بن يحيى أخبرنا ابن وهب أخبرني يونس عن ابن شهاب قال حدثني سالم بن عبد الله أن

عبد الله بن عمر رضي الله عنهما قال

سمعت رسول الله ﷺ يقول إذا رأيتموه فصوموا وإذا رأيتموه فأفطروا فإن غم عليكم فاقدروا له

مسلم 2504صحيح
Contents
Reference
Commentary
Ayat
Collection
Sahih Muslim
Book
Fasting
Chapter
Obligation of fasting Ramadan upon sighting Hilal and breaking the fast upon sighting Hilal, and that if it is obscured at its beginning or end the month is completed as thirty days
Numbering
Darussalam 2504
Muslim 2504