A ransom. From fida’, “to ransom,” “to exchange.” An expiation for sin, or for the duties unperformed. The word occurs three times in the Qur’an: –
Surah ii 180: “For those who are able to keep it (the fast) and yet break it, there shall be as an expiatos the maintenance of a poor man.”
Surah ii 192: “Perform the pilgrimage and the visitation of the holy places…But whoever among you is sick, or hath an ailment of the head, must expiate by fasting, or alms, or a sacrifice.”
Surah lvii 14: “On that day (the Day of Judgement) so expiation shall be taken from you (i.e. the hypocrites) or from those who do not believe; your abode is the fire.
The other word used in the Qur’an for the same idea is kaffarah. [KAFFARAH, EXPIATION.]
Based on Hughes, Dictionary of Islam