Sadaqa

Sadaqa is voluntary Islamic charity as opposed to zakat, or obligatory charity. Sadaqa may be financial assistance, public service, or even a smile to someone who needs it. It is often the social norm to give ""Sadaqa"" when visiting sites holy to Islam or making pilgrimage.
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Legally prescribed alms tax

Sadaqa: (singular:) charity offered voluntarily; its plural is: sadaqat