KAFFARAH كفارة
From kafr, “to hide.” Heb. Lit. “Coverings; atonements; expiation.”
The word occurs four times in the Qur’an:-
Surah v. 49: “Whoso remitteth it as alms shall have expiation for his sins.”
Surah v. 91: “Its expiation shall be to feed ten persons.” “This is the expiation for your oaths.”
Surah v. 96: “In expiation thereof shall ye feed the poor.”
The other word used is fidyah [FIDYAH]. The expression kaffaratu ‘z-zunub, “atonement for sins,” is used for expiation by prayer, alms, fasting, and pilgrimage. [EXPIATION.]

Based on Hughes, Dictionary of Islam