Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
suyuti:2-3503bSlm
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السيوطي:٢-٣٥٠٣b

"عن أسلم: أن عمر بن الخطاب أفطر ذات يوم في رمضان في يوم غيم، ورأى أنه قد أمسى وغابت الشمس، فجاءه رجل فقال: يا أمير المؤمنين! قد طلعت الشمس، فقال عمر: الخطب يسير وقد اجتهدنا".  

مالك

See similar narrations below:

Collected by Mālik, Suyūṭī
malik:18-49Yaḥyá > Mālik > Zayd b. Aslam > Akhīh Khālid b. Aslam

Yahya related to me from Malik from Zayd ibn Aslam from his brother Khalid ibn Aslam that Umar ibn al-Khattab once broke thefast on a cloudy day thinking that evening had come and the sun had set. Then a man came to him and said, "Amir al-muminin, the sun has come out,'' and Umar said, "That's an easy matter. It was our deduction (ijtihad)." Malik said, "According to what we think, and Allah knows best, what he was referring to when he said, 'That's an easy matter' was making up the fast, and how slight the effort involved was and how easy it was. He was saying (in effect), 'We will fast another day in its place.' "  

مالك:١٨-٤٩حَدَّثَنِي يَحْيَى عَنْ مَالِكٍ عَنْ زَيْدِ بْنِ أَسْلَمَ عَنْ أَخِيهِ خَالِدِ بْنِ أَسْلَمَ

أَنَّ عُمَرَ بْنَ الْخَطَّابِ أَفْطَرَ ذَاتَ يَوْمٍ فِي رَمَضَانَ فِي يَوْمٍ ذِي غَيْمٍ وَرَأَى أَنَّهُ قَدْ أَمْسَى وَغَابَتِ الشَّمْسُ فَجَاءَهُ رَجُلٌ فَقَالَ يَا أَمِيرَ الْمُؤْمِنِينَ طَلَعَتِ الشَّمْسُ فَقَالَ عُمَرُ الْخَطْبُ يَسِيرٌ وَقَدِ اجْتَهَدْنَا قَالَ مَالِكٌ يُرِيدُ بِقَوْلِهِ الْخَطْبُ يَسِيرٌ الْقَضَاءَ فِيمَا نُرَى وَاللَّهُ أَعْلَمُ وَخِفَّةَ مَؤُونَتِهِ وَيَسَارَتِهِ يَقُولُ نَصُومُ يَوْمًا مَكَانَهُ  

suyuti:2-1219bSlam
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السيوطي:٢-١٢١٩b

"عَنْ أسْلَمَ أَنَّ عَمرَ بنَ الخطابِ أفْطر ذاتَ يَوْمٍ في رمضانَ في يومٍ ذى غَيْمٍ، وَرَأَى أَنَّهُ قَدْ أمسى وَغَابَتِ الشَّمْسُ، فَجاءَهُ رجل، فقال: يا أميرَ المؤمنينَ: قَدْ طَلَعتِ الشَّمْسُ، فقال عُمَرُ: الخَطْبُ يَسِيرٌ، وقَدِ اجتَهدْنا".  

مالك، والشافعى، [ق] البيهقى في السنن