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Hadith #2312990
hasan· Al-Albani

Zayd ibn Thabit reported that 'Umar ibn al-Khattab came to him to ask to see him one day and he gave him permission while his head was in the hands of a slavegirl of his who was combing his hair. He removed his head and 'Umar said to him, 'Let her comb it.' He said, 'Amir al-Mu'minin, if you were to send for me, I would come to you.' ''Umar said, 'It is my need.'"

حَدَّثَنَا مُحَمَّدٌ، قَالَ‏:‏ أَخْبَرَنَا عَبْدُ اللهِ، قَالَ‏:‏ حَدَّثَنَا يَحْيَى بْنُ أَيُّوبَ قَالَ‏:‏ حَدَّثَنِي عُقَيْلُ بْنُ خَالِدٍ، أَنَّ سَعِيدَ بْنَ سُلَيْمَانَ بْنِ زَيْدِ بْنِ ثَابِتٍ حَدَّثَهُ، عَنْ أَبِيهِ، عَنْ جَدِّهِ زَيْدِ بْنِ ثَابِتٍ، أَنَّ عُمَرَ بْنَ الْخَطَّابِ جَاءَهُ يَسْتَأْذِنُ عَلَيْهِ يَوْمًا، فَأَذِنَ لَهُ وَرَأْسُهُ فِي يَدِ جَارِيَةٍ لَهُ تُرَجِّلُهُ، فَنَزَعَ رَأْسَهُ، فَقَالَ لَهُ عُمَرُ‏:‏ دَعْهَا تُرَجِّلُكَ، فَقَالَ‏:‏ يَا أَمِيرَ الْمُؤْمِنِينَ، لَوْ أَرْسَلْتَ إِلَيَّ جِئْتُكَ، فَقَالَ عُمَرُ‏:‏ إِنَّمَا الْحَاجَةُ لِي‏.‏

References2 variants
Sunnah.com reference
Book 55, Hadith 21
Arabic/English book reference
Book 55, Hadith 1302