Sadaqah

[2] 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.

It is also a cognate of the Jewish concept of tzedakah, a Hebrew word that also refers to acts of voluntary giving.

[2] In Islamic terminology, sadaqah has been defined as an act of "giving something... without seeking a substitute in return and with the intention of pleasing Allah.

[6] The three-letter root of this word, s-d-q, also means, "to speak the truth", "to be sincere", and "to fulfill one's promise".

The Quran criticizes donations aimed at appearing generous and compromising the value of sadaqa through ostentatious public behavior, which renders a normally charitable act purely self-serving.

[8] Among the many verses on sadaqat, either voluntary or obligatory, are these: According to some ahadith, "a kind word and smile" can be considered as sadaqa and the best form of it is "passing on knowledge.

Among the differences between them is that in the case of zakat, the amount is fixed, utilized according to that which has been stated by the Islamic Law, and paid only once a year.