Hadhrat Zainab (Radhiyallaho anha) was the next to be married to the Prophet Mohammad (Sallallaho Alaihe Wasallam) . There are divergent reports about her previous husbands. According to one report she was first married to Hadhrat Abdullah bin Jahsh (Radhiyallaho anho) who was killed in Uhud, as we have already seen in his story in chapter VII. According to another report, she was first married to Tufail ibnul al Harith and when divorced by him was remarried to his brother Ubaidah ibnul Harith, who was killed in Badr.
The Prophet Mohammad (Sallallaho Alaihe Wasallam) married her in Ramadan 3 A.H. She lived with the Prophet Mohammad (Sallallaho Alaihe Wasallam) for eight months only, as she died in Rabi-ul-Akhir, 4 A.H. Hadhrat Zainab and Hadhrat Khadijah (Radhiyallaho anha) are the two wives of the Prophet Mohammad (Sallallaho Alaihe Wasallam) who died during his life time. All the other wives lived on after him and died later. Hadhrat Zainab (Radhiyallaho anha) spent very liberally on the poor, and was Ummul Masakin’ (mother of the poor) even before Islam.
Source : eislam