صحيح البخاري Sahih Bukhari كتاب الصوم The Book of As-Saum (The Fasting).
بَابُ مَتَى يَحِلُّ فِطْرُ الصَّائِمِ:

(43) Chapter. When should the person observing Saum (fast) break his Saum (fast)?

2 hadith
Hadith 1954
حَدَّثَنَا الْحُمَيْدِيُّ ، حَدَّثَنَا سُفْيَانُ ، حَدَّثَنَا هِشَامُ بْنُ عُرْوَةَ ، قَالَ : سَمِعْتُ أَبِي ، يَقُولُ : سَمِعْتُ عَاصِمَ بْنَ عُمَرَ بْنِ الْخَطَّابِ ، عَنْ أَبِيهِ رَضِيَ اللَّهُ عَنْهُ ، قَالَ : قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ : " إِذَا أَقْبَلَ اللَّيْلُ مِنْ هَاهُنَا ، وَأَدْبَرَ النَّهَارُ مِنْ هَاهُنَا ، وَغَرَبَتِ الشَّمْسُ ، فَقَدْ أَفْطَرَ الصَّائِمُ " .
Narrated `Umar bin Al-Khattab: Allah's Apostle said, "When night falls from this side and the day vanishes from this side and the sun sets, then the fasting person should break his fast."
Hadith Reference Sahih Bukhari / The Book of As-Saum (The Fasting). / Hadith: 1954
Hadith Grading محدثین: أحاديث صحيح البخاريّ كلّها صحيحة
Hadith 1955
حَدَّثَنَا إِسْحَاقُ الْوَاسِطِيُّ حَدَّثَنَا خَالِدٌ عَنْ الشَّيْبَانِيِّ عَنْ عَبْدِ اللَّهِ بْنِ أَبِي أَوْفَى رَضِيَ اللَّهُ عَنْهُ قَالَ كُنَّا مَعَ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فِي سَفَرٍ وَهُوَ صَائِمٌ فَلَمَّا غَرَبَتْ الشَّمْسُ قَالَ لِبَعْضِ الْقَوْمِ يَا فُلَانُ 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 صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ ثُمَّ قَالَ إِذَا رَأَيْتُمْ اللَّيْلَ قَدْ أَقْبَلَ مِنْ هَا هُنَا فَقَدْ أَفْطَرَ الصَّائِمُ.
Narrated `Abdullah bin Abi `Aufa: We were in the company of the Prophet 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 said, "Get down and mix Sawiq with water for us." He replied, "O Allah's Apostle! (If you wait) till it is evening." The Prophet said again, "Get down and mix Sawiq with water for us." He replied, "It is still daytime."(1) The Prophet said again, "Get down and mix Sawiq with water for us." He got down and mixed Sawiq for them. The Prophet drank it and then said, "When you see night falling from this side, the fasting person should break his fast."
Hadith Reference Sahih Bukhari / The Book of As-Saum (The Fasting). / Hadith: 1955
Hadith Grading محدثین: أحاديث صحيح البخاريّ كلّها صحيحة