Ṣadaqah in the modern-day Islamic context has come to signify "voluntary charity". Unlike zakat, which is a obligatory form of almsgiving and one of the five pillars of Islam, ṣadaqah is a voluntary offering whose amount and nature are determined solely by the benefactor, as emphasized in the Quran.
According to the Quran, the word means a voluntary offering, whose amount is at the will of the benefactor. It is similar to zakat, or compulsory giving, one of the five pillars of Islam.
It is also a cognate of the Jewish concept of tzedakah, a Hebrew word that also refers to acts of voluntary giving.