Sayyidah Aishah (may Allah be pleased with her) said that the Messenger of Allah (peace and blessings be upon him) said: "Those (heirs) who seek to kill in retaliation must hold back, the first and then the next, even if it be a woman."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 16070
Abu Ubayd (may Allah have mercy on him) said concerning the hadith of the Prophet (peace and blessings be upon him) about the family of the slain, "that they should hold back, the nearest and then the next nearest, even if it be a woman": This means that a man is killed and he has heirs, men and women. He says: whichever of them, the nearest and then the next nearest, man or woman, pardons his blood, his pardon is valid, because his word yanhajizu means "they should refrain from retaliation."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 16071
Zayd bin Wahb (may Allah have mercy on him) said: A man saw another man with his wife and killed her. The case was brought to Sayyiduna Umar (may Allah be pleased with him). Some of the slain woman's brothers gave up their share as charity, so Sayyiduna Umar (may Allah be pleased with him) ordered blood money for the rest of them.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 16072
Zayd bin Wahb al-Juhani (may Allah have mercy on him) said: A man killed his wife; the woman's three brothers sought retribution, and the case came before Sayyiduna Umar (may Allah be pleased with him). One brother pardoned, so he (may Allah be pleased with him) said to the remaining two: Take two-thirds of the blood money; there is now no way to kill him.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 16073
Ibrahim al-Nakha'i (may Allah have mercy on him) said: The case of a man who had committed deliberate killing was brought to Sayyiduna Umar (may Allah be pleased with him). Some of the heirs pardoned him before Sayyiduna Umar (may Allah be pleased with him), but Sayyiduna Umar (may Allah be pleased with him) still ordered that he be killed. Sayyiduna Ibn Mas'ud (may Allah be pleased with him) saw this and said: These are all his heirs, and some of them have pardoned, so how can he be killed? Sayyiduna Umar (may Allah be pleased with him) asked: Then what is your view? He said: Let blood money be imposed; leaving out the share that has been pardoned, the rest of the blood money should be taken. Sayyiduna Umar (may Allah be pleased with him) said: That is my judgement too.
This is munqati' (broken), and the connected narration before it supports it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 16074