When Salim (may Allah be pleased with him) was killed, they said: a quarter of the Quran has gone

It is narrated from Sayyiduna Urwah bin al-Zubayr (may Allah be pleased with him) that Umm Salim al-Ansariyyah, the mistress of Salim, the freed slave of Abu Hudhayfah, freed Salim purely for the pleasure of Allah (so that she would retain no right of inheritance over him). Then, when he was martyred in the Battle of Yamamah, he left a weapon and a horse as his estate. Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) sent a message to that woman: Take this estate, for you are the most entitled of people to it. She replied: I have no need of it; I left him for Allah at the very time I freed him. So Sayyiduna Umar (may Allah be pleased with him) took those belongings and dedicated them to the path of Allah (for the fighters).

It is narrated from Sayyiduna Zayd bin Thabit (may Allah be pleased with him) that he said: When Salim, the freed slave of Abu Hudhayfah, was martyred (in the Battle of Yamamah), the Companions said: Today a quarter of the knowledge of the Qur'an has departed.
This hadith is sahih (authentic) on the condition of the two Shaykhs.