Continuous charity is considered endowment
4-2-2014 | IslamWeb
Question:
Is it a condition for continuous charity that it is done by a person before his death? For example, should he build a mosque before his death? Is it permissible for his parents, brothers, children or wife to do this charity such as building a mosque or presenting copies of the Quran for the mosque on behalf of the dead person? According to my humble information, ordinary charity is like giving money once or more on behalf of the dead. However, continuous charity should continue, such as building a mosque, hospital, endowment, and so on, whether the person endowed it before his death, stated that in the bequest or it was done by his relatives after his death. What is the criterion to differentiate between ordinary and continuous charity on behalf of the dead person? How can the relatives of the dead pay continuous charity on his behalf?
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
Continuous charity is stated in the narrated hadith by Abu Hurayrah 
in which it was stated that the Prophet, sallallaahu ‘alayhi wa sallam, said: “When a person dies, his deeds come to an end, except for three: a continuous charity, knowledge from which people benefit, and a pious son who prays for him.” [Muslim]
Some scholars interpreted continuous charity to mean endowment because the basis is kept and the benefit is given in charity. So, the basis of endowment remains undiminished and that is why it is called continuous charity. Zakariyya Al-Ansaari, a Shaafi‘i scholar 
said, “Continuous charity is interpreted by some scholars to mean endowment as Ar-Raafi‘i said, ‘It does not mean bequest of giving the yields of things in charity because it is rare.'”
This kind of endowment is not conditioned with being done by the person himself. Rather, its reward returns to him even if it is endowed by another person. Zakariyya Al-Ansaari, may Allaah have Mercy upon him, said, “Prayer for the dead person, whether from an heir or a non-heir will benefit the dead. Similarly, endowment and charity on his behalf, building mosques, digging wells, and so on – on his behalf as charity – will benefit him like any deed he did during his life.”
Non-continuous charity is whatever is given in charity without retaining its basis, such as giving some money in charity.
Allaah Knows best.