Sahih al-Bukhari 30:65
Narrated Ibn Abi `Aufa:
I was with the Prophet (ﷺ) on a journey, and he observed the fast till evening. The Prophet (ﷺ) said to a man, "Get down and mix Sawiq with water for me." He replied, "Will you wait till it is evening?" The Prophet said, "Get down and mix Sawiq with water for me; when you see night falling from this side, the fasting person should break his fast."
Reference
Sahih al-Bukhari 30:65
In-book reference
Book 30, Hadith 65
Arabic Text
حَدَّثَنَا أَحْمَدُ بْنُ يُونُسَ، حَدَّثَنَا أَبُو بَكْرٍ، عَنْ سُلَيْمَانَ، عَنِ ابْنِ أَبِي أَوْفَى ـ رضى الله عنه ـ قَالَ كُنْتُ مَعَ النَّبِيِّ صلى الله عليه وسلم فِي سَفَرٍ، فَصَامَ حَتَّى أَمْسَى، قَالَ لِرَجُلٍ " انْزِلْ، فَاجْدَحْ لِي ". قَالَ لَوِ انْتَظَرْتَ حَتَّى تُمْسِيَ. قَالَ " انْزِلْ، فَاجْدَحْ لِي، إِذَا رَأَيْتَ اللَّيْلَ قَدْ أَقْبَلَ مِنْ هَا هُنَا فَقَدْ أَفْطَرَ الصَّائِمُ ".