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كتاب الصوم
30  
Fasting
(43)
Chapter: When to break the Saum (fast)?
(43)
باب مَتَى يَحِلُّ فِطْرُ الصَّائِمِ
Sahih al-Bukhari 1955

Narrated `Abdullah bin Abi `Aufa:

We were in the company of the Prophet (ﷺ) on a journey and he was fasting, and when the sun set, he addressed somebody, "O so-and-so, get up and mix Sawiq with water for us." He replied, "O Allah's Apostle! (Will you wait) till it is evening?" The Prophet (ﷺ) said, "Get down and mix Sawiq with water for us." He replied, "O Allah's Messenger (ﷺ)! (If you wait) till it is evening." The Prophet (ﷺ) said again, "Get down and mix Sawiq with water for us." He replied, "It is still daytime."(1) The Prophet (ﷺ) said again, "Get down and mix Sawiq with water for us." He got down and mixed Sawiq for them. The Prophet (ﷺ) drank it and then said, "When you see night falling from this side, the fasting person should break his fast."

حَدَّثَنَا إِسْحَاقُ الْوَاسِطِيُّ، حَدَّثَنَا خَالِدٌ، عَنِ الشَّيْبَانِيِّ، عَنْ عَبْدِ اللَّهِ بْنِ أَبِي أَوْفَى ـ رضى الله عنه ـ قَالَ كُنَّا مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم فِي سَفَرٍ، وَهُوَ صَائِمٌ، فَلَمَّا غَرَبَتِ الشَّمْسُ قَالَ لِبَعْضِ الْقَوْمِ ‏"‏ يَا فُلاَنُ قُمْ، فَاجْدَحْ لَنَا ‏"‏‏.‏ فَقَالَ يَا رَسُولَ اللَّهِ، لَوْ أَمْسَيْتَ‏.‏ قَالَ ‏"‏ انْزِلْ، فَاجْدَحْ لَنَا ‏"‏‏.‏ قَالَ يَا رَسُولَ اللَّهِ فَلَوْ أَمْسَيْتَ‏.‏ قَالَ ‏"‏ انْزِلْ، فَاجْدَحْ لَنَا ‏"‏‏.‏ قَالَ إِنَّ عَلَيْكَ نَهَارًا‏.‏ قَالَ ‏"‏ انْزِلْ، فَاجْدَحْ لَنَا ‏"‏‏.‏ فَنَزَلَ فَجَدَحَ لَهُمْ، فَشَرِبَ النَّبِيُّ صلى الله عليه وسلم ثُمَّ قَالَ ‏"‏ إِذَا رَأَيْتُمُ اللَّيْلَ قَدْ أَقْبَلَ مِنْ هَا هُنَا، فَقَدْ أَفْطَرَ الصَّائِمُ ‏"‏‏.‏
Reference : Sahih al-Bukhari 1955
In-book reference : Book 30, Hadith 62
USC-MSA web (English) reference : Vol. 3, Book 31, Hadith 176
  (deprecated numbering scheme)