Sahih Bukhari Volume 3, Book 30, Hadith 1957

حَدَّثَنَا مُسَدَّدٌ، حَدَّثَنَا عَبْدُ الْوَاحِدِ، حَدَّثَنَا الشَّيْبَانِيُّ، قَالَ سَمِعْتُ عَبْدَ اللَّهِ بْنَ أَبِي أَوْفَى ـ رضى الله عنه ـ قَالَ سِرْنَا مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم وَهْوَ صَائِمٌ، فَلَمَّا غَرَبَتِ الشَّمْسُ قَالَ ‏"‏ انْزِلْ، فَاجْدَحْ لَنَا ‏"‏‏.‏ قَالَ يَا رَسُولَ اللَّهِ، لَوْ أَمْسَيْتَ‏.‏ قَالَ ‏"‏ انْزِلْ، فَاجْدَحْ لَنَا ‏"‏‏.‏ قَالَ يَا رَسُولَ اللَّهِ، إِنَّ عَلَيْكَ نَهَارًا‏.‏ قَالَ ‏"‏ انْزِلْ، فَاجْدَحْ لَنَا ‏"‏‏.‏ فَنَزَلَ، فَجَدَحَ، ثُمَّ قَالَ ‏"‏ إِذَا رَأَيْتُمُ اللَّيْلَ أَقْبَلَ مِنْ هَا هُنَا فَقَدْ أَفْطَرَ الصَّائِمُ ‏"‏‏.‏ وَأَشَارَ بِإِصْبَعِهِ قِبَلَ الْمَشْرِقِ

Narrated By 'Abdullah bin Abi Aufa : We were travelling with Allah's Apostle and he was fasting, and when the sun set, he said to (someone), "Get down and mix Sawiq with water for us." He replied, "O Allah's Apostle! (Will you wait) till it is evening?" The Prophet again said, "Get down and mix Sawiq with water for us." He replied, "O Allah's Apostle! It is still daytime." The Prophet said again, "Get down and mix Sawiq with water for us." So, he got down and carried out that order. The Prophet then said, "When you see night falling from this side, the fasting person should break his fast," and he beckoned with his finger towards the east.