Fast when seeing new crescent and calculate if not seen

This hadith speaks about the importance of fasting in Islam. It was narrated by Ibn 'Umar that Prophet Muhammad said that when you see the new crescent, you should fast and when it disappears, you should stop fasting. If there are clouds covering it, then one should calculate thirty days as a sign of completion of a month. Ibn 'Umar used to fast one day before seeing the new crescent as an act of precautionary measure. This hadith teaches us to be mindful and conscious about our religious obligations such as fasting during Ramadan or any other time prescribed by Islamic law. It also encourages us to be proactive in fulfilling our religious duties even if we cannot physically see them due to certain circumstances like cloudy weather or any other reason.