Al-Matalib al-'Aliyah 4108 — The virtue of Umm Waraqah

It is narrated from Sayyidah Umm Waraqah bint Abdullah bin al-Harith al-Ansariyyah (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) used to go to visit her and would call her by the honoured title "al-Shahidah" (the one who will be martyred). Along with memorising the Noble Qur'an, she had also collected the hadith of the Prophet. Then (after her martyrdom) Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) stood among the people and said: "Umm Waraqah has been killed by her slave and her slave girl, who strangled her with a cloth, and the two of them have fled." So the two culprits were caught and brought, and they were crucified. On this occasion Sayyiduna Umar (may Allah be pleased with him) said: "The Messenger of Allah (peace and blessings be upon him) spoke the truth; he (peace and blessings be upon him) often used to say (to us): 'Come, let us go and visit the Shahidah (the martyr).'"
Imam Abu Dawud recorded a part of this hadith, apart from the (detailed) incident which I have mentioned here.