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suyuti:2-1321bZayd b. Aslam Sharb ʿUmar Laban Faʾaʿjabah Fasaʾal al--Adhá Saqāh from Ayn Lak Hadhā al-Laban
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السيوطي:٢-١٣٢١b

"عَنْ زَيْدٍ بْنِ أَسْلَمَ: شَربَ عُمَرُ لَبَنًا فَأَعْجَبَهُ، فَسَأَلَ الَّذى سَقَاهُ مِنْ أَيْنَ لَك هَذَا اللَّبَنُ؟ فَأَخْبَرَهُ أنَّهُ وَرَدَ عَلَى مَاءٍ فَإِذَا نَعَمٌ مِنْ نَعَمِ الصَّدَقَةِ وَهُمْ يَسْقُونَ، فحَلَبُوا لَنَا مِنْ أَلْبَانِهَا فَجَعَلتُهُ فِى سِقَائِى هَذَا، فَأَدْخَلَ عُمَرُ أُصْبَعَهُ فَاسْتَقَاءَهُ".  

مالك، [ق] البيهقى في السنن

See similar narrations below:

Collected by Bayhaqī
bayhaqi:13164Abū Aḥmad ʿAbdullāh b. Muḥammad b. al-Ḥasan al-ʿAdl > Abū Bakr Muḥammad b. Jaʿfar al-Muzakkī > Muḥammad b. Ibrāhīm al-ʿAbdī > Ibn Bukayr > Mālik > Zayd b. Aslam > Sharib ʿUmar b. al-Khaṭṭāb Laban Faʾaʿjabah Fasaʾal al--Adhī Saqāh from Ayn Lak Hadhā al-Laban Faʾakhbarah > And Rad

[Machine] He informed him that he returned to a water which he named, so it turned out to be a type of charity. And they were giving it to drink, so they milked it for me and I placed it in my container. Then Umar, may Allah be pleased with him, put his finger in it and tasted it.  

البيهقي:١٣١٦٤أَخْبَرَنَا أَبُو أَحْمَدَ عَبْدُ اللهِ بْنِ مُحَمَّدِ بْنِ الْحَسَنِ الْعَدْلُ أنبأ أَبُو بَكْرٍ مُحَمَّدُ بْنُ جَعْفَرٍ الْمُزَكِّي ثنا مُحَمَّدُ بْنُ إِبْرَاهِيمَ الْعَبْدِيُّ ثنا ابْنُ بُكَيْرٍ ثنا مَالِكٌ عَنْ زَيْدِ بْنِ أَسْلَمَ أَنَّهُ قَالَ شَرِبَ عُمَرُ بْنُ الْخَطَّابِ ؓ لَبَنًا فَأَعْجَبَهُ فَسَأَلَ الَّذِي سَقَاهُ مِنْ أَيْنَ لَكَ هَذَا اللَّبَنُ؟

فَأَخْبَرَهُ أَنَّهُ وَرَدَ عَلَى مَاءٍ قَدْ سَمَّاهُ فَإِذَا نَعَمٌ مِنْ نَعَمِ الصَّدَقَةِ وَهُمْ يَسْقُونَ فَحَلَبُوا لِي مِنْ أَلْبَانِهَا فَجَعَلْتُهُ فِي سِقَائِي هَذَا فَأَدْخَلَ عُمَرُ ؓ أُصْبُعَهُ فِي فِيهِ وَاسْتَقَاءَهُ