Sa'id bin al-Musayyib (may Allah have mercy on him) said that Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) executed five or seven men in retaliation for one man whom they had killed by treachery, and he said: If all the people of Sana'a had taken part in killing him, I would have killed them all.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 15973