Muwatta Malik #1710
Blood-Money
The Arabic includes the chain of narration (sanad) and the collector's commentary; the English translation shows the Prophet's words only.
وَحَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ يَحْيَى بْنِ سَعِيدٍ، عَنْ سَعِيدِ بْنِ الْمُسَيَّبِ، أَنَّ عُمَرَ بْنَ الْخَطَّابِ، قَتَلَ نَفَرًا خَمْسَةً أَوْ سَبْعَةً بِرَجُلٍ وَاحِدٍ قَتَلُوهُ قَتْلَ غِيلَةٍ وَقَالَ عُمَرُ لَوْ تَمَالأَ عَلَيْهِ أَهْلُ صَنْعَاءَ لَقَتَلْتُهُمْ جَمِيعًا .
Yahya related to me from Malik from Yahya ibn Said from Said ibn
al-Musayyab that Umar ibn al-Khattab killed five or seven people for
one man whom they had killed secretly by trickery. Umar said, "Had all
the people of Sana joined forces against him, I would have killed them
all."
About Muwatta Malik
This hadith is #1710 from Muwatta Malik, in the Book of Blood-Money.