"the Messenger of Allah said: 'Fast when you see it and stop fasting when you see it, and if it is obscured from you (too cloudy), then count it as thirty (days). "' (Using translation from Nasāʾī 2117)

عَنْ رَسُولِ اللَّهِ ﷺ قَالَ «صُومُوا لِرُؤْيَتِهِ وَأَفْطِرُوا لِرُؤْيَتِهِ فَإِنْ غُمَّ عَلَيْكُمْ فَصُومُوا ثَلَاثِينَ»