Messenger of Allah ﷺ said, "The month (can be) 29 nights (i.e. days), and do not fast till you see the moon, and if the sky is overcast, then complete Sha'ban as thirty days."
أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ الشَّهْرُ تِسْعٌ وَعِشْرُونَ لَيْلَةً فَلاَ تَصُومُوا حَتَّى تَرَوْهُ فَإِنْ غُمَّ عَلَيْكُمْ فَأَكْمِلُوا الْعِدَّةَ ثَلاَثِينَ
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.
قَالَ رَسُولُ اللَّهِ ﷺ إِنَّمَا الشَّهْرُ تِسْعٌ وَعِشْرُونَ فَلاَ تَصُومُوا حَتَّى تَرَوْهُ وَلاَ تُفْطِرُوا حَتَّى تَرَوْهُ فَإِنْ غُمَّ عَلَيْكُمْ فَاقْدِرُوا لَهُ
The month may consist of twenty-nine nights. So do not fast till you have sighted it (the new moon) and do not break it till you have sighted it, except when the sky is cloudy for you, and if it is so, then calculate it.
قَالَ رَسُولُ اللَّهِ ﷺ الشَّهْرُ تِسْعٌ وَعِشْرُونَ لَيْلَةً لاَ تَصُومُوا حَتَّى تَرَوْهُ وَلاَ تُفْطِرُوا حَتَّى تَرَوْهُ إِلاَّ أَنْ يُغَمَّ عَلَيْكُمْ فَإِنْ غُمَّ عَلَيْكُمْ فَاقْدِرُوا لَهُ
Yahya related to me from Malik from Abdullah ibn Dinar from Abdullah ibn Umar that the Messenger of Allah ﷺ said, "A month has twenty-nine days in it. Do not start the fast or break it until you see the new moon. If the new moon is obscured from you, then work out (when it should be)."
أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ الشَّهْرُ تِسْعٌ وَعِشْرُونَ فَلاَ تَصُومُوا حَتَّى تَرَوُا الْهِلاَلَ وَلاَ تُفْطِرُوا حَتَّى تَرَوْهُ فَإِنْ غُمَّ عَلَيْكُمْ فَاقْدُرُوا لَهُ
Yahya related to me from Malik from Thawr ibn Zayd ad-Dili from Abdullah ibn Abbas that the Messenger of Allah ﷺ once mentioned Ramadan and said, "Do not start the fast or break it until you see the new moon. If the new moon is obscured from you, then complete a full thirty days."
أَنَّ رَسُولَ اللَّهِ ﷺ ذَكَرَ رَمَضَانَ فَقَالَ لاَ تَصُومُوا حَتَّى تَرَوُا الْهِلاَلَ وَلاَ تُفْطِرُوا حَتَّى تَرَوْهُ فَإِنْ غُمَّ عَلَيْكُمْ فَأَكْمِلُوا الْعِدَّةَ ثَلاَثِينَ
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»
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)
أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ «إِنَّمَا الشَّهْرُ تِسْعٌ وَعِشْرُونَ فَلَا تَصُومُوا حَتَّى تَرَوْهُ وَلَا تُفْطِرُوا حَتَّى تَرَوْهُ فَإِنْ أُغْمِيَ عَلَيْكُمْ فَاقْدُرُوا لَهُ»
"لَا تَصُومُوا حَتَّى تَرَوا الهِلَال، فإِنْ غُمَّ عَلَيكُم فَأَكْمِلُوا العِدَّةَ ثَلَاثِينَ".
"الشَّهْرُ تسعٌ وعِشْرُونَ فَلَا تَصُوموا حَتَّى تَرَوْهُ ولا تُفْطِرُوا حَتَّى تَرَوْهُ، فإِنْ غُمَّ عَلَيكم فأَكْمِلُوا العِدَّةَ ثَلاثينَ".