"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»
"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»
" 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»
A bedouin came to the Prophet ﷺ and said: I have sighted the moon. Al-Hasan added in his version: that is, of Ramadan. He asked: Do you testify that there is no god but Allah? He replied: Yes. He again asked: Do you testify that Muhammad is the Messenger of Allah? He replied: Yes. and he testified that he had sighted the moon. He said: Bilal, announce to the people that they must fast tomorrow. (Using translation from Abū Dāʾūd 2340)
جَاءَ أَعْرَابِيٌّ إِلَى النَّبِيِّ ﷺ وَقَالَ إِنِّي رَأَيْتُ الْهِلَالَ فَقَالَ «أَتَشْهَدُ أَنْ لَا إِلَهَ إِلَّا اللَّهُ وَأَنِّي رَسُولُ اللَّهِ؟» قَالَ نَعَمْ قَالَ «يَا بِلَالُ نَادِ فِي النَّاسِ فَلْيَصُومُوا غَدًا»
The people looked for the moon, so I informed the Messenger of Allah ﷺ that I had sighted it. He fasted and commanded the people to fast. (Using translation from Abū Dāʾūd 2342)
«تَرَاءَى النَّاسُ الْهِلَالَ فَأَخْبَرْتُ رَسُولَ اللَّهِ ﷺ أَنِّي رَأَيْتُهُ فَصَامَ وَأَمَرَ النَّاسَ بِالصِّيَامِ»
The month of Ramadan may consist of twenty-nine days. So do not fast till you have sighted it (the new moon) and do not break fast, till you have sighted it (the new moon of Shawwal), and if the sky is cloudy for you, then calculate. (Using translation from Muslim 1080e)
قَالَ رَسُولُ اللَّهِ ﷺ «إِنَّمَا الشَّهْرُ تِسْعٌ وَعِشْرُونَ فَلَا تَصُومُوا حَتَّى تَرَوْهُ وَلَا تُفْطِرُوا حَتَّى تَرَوْهُ فَإِنْ غُمَّ عَلَيْكُمْ فَاقْدُرُوا لَهُ»