حَدَّثَنَا عَبْدُ الرَّحْمَنِ حَدَّثَنَا مَالِكٌ عَنْ نَافِعٍ عَنِ ابْنِ عُمَرَ عَنْ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ لَا تَصُومُوا حَتَّى تَرَوْا الْهِلَالَ وَلَا تُفْطِرُوا حَتَّى تَرَوْهُ فَإِنْ غُمَّ عَلَيْكُمْ فَاقْدُرُوا لَهُ
مسند امام احمد بن حنبل · Hadith 5294
It was narrated from Ibn 'Umar that the Prophet (PBUH) said: "Do not fast until you see the new moon and do not break the fast until you see it, and if it is cloudy, then work it out."
Translated by Dr. Muhammad Muhsin Khan · Reviewed by Islamic University of Madinah · Published March 2020