"Do not fast until you see the crescent, and do not stop fasting until you see it, and if it is obscured from you (too cloudy), then work it out." (Using translation from Nasāʾī 2121)  

أَنَّ رَسُولَ اللَّهِ ﷺ ذَكَرَ رَمَضَانَ فَقَالَ «لَا تَصُومُوا حَتَّى تَرَوْا الْهِلَالَ وَلَا تُفْطِرُوا حَتَّى تَرَوْهُ فَإِنْ غُمَّ عَلَيْكُمْ فَاقْدُرُوا لَهُ»  

"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)  

قَالَ رَسُولُ اللَّهِ ﷺ أَوْ قَالَ أَبُو الْقَاسِمِ ﷺ «صُومُوا لِرُؤْيَتِهِ وَأَفْطِرُوا لِرُؤْيَتِهِ فَإِنْ غُمَّ عَلَيْكُمُ الشَّهْرُ فَعُدُّوا ثَلَاثِينَ»  

" I am surprised at those who anticipate the moth, when the Messenger of Allah said: 'When you see the new crescent then fast, and when you see it, then stop fasting, and if it is obscured from you (too cloudy), then complete thirty days. (Using translation from Nasāʾī 2125)  

قَالَ رَسُولُ اللَّهِ ﷺ «إِذَا رَأَيْتُمُوهُ فَصُومُوا وَإِذَا رَأَيْتُمُوهُ فَأَفْطِرُوا فَإِنْ غُمَّ عَلَيْكُمْ فَأَكْمِلُوا الْعِدَّةَ ثَلَاثِينَ يَوْمًا»