question #3 Sahih Muslim 1088b, Book 13, Hadith 36 : What guidance did the Prophet Muhammad (ﷺ) provide regarding the completion of the lunar month when the moon is not visible?

We saw the new moon of Ramadan as we were at Dhit-i-‘Irq. We sent a man to Ibn Abbas (Allah be pleased with both of them) to ask him (whether the sighting of a small moon had something of the nature of defect in it). Upon this Ibn ‘Abbas (Allah be pleased with both of them) said that the Messenger of Allah (ﷺ) had said: Verily Allah deferred its sight, but if (the new moon) is hidden from you, then, complete its number (thirty).