Appears 2 times in the Quran. (Root: تبع)
  1. And it does not behoove a believer to kill a believer except by mistake, and whoever kills a believer by mistake, he should free a believing slave, and blood-money should be paid to his people unless they remit it as alms; but if he be from a tribe hostile to you and he is a believer, the freeing of a believing slave (suffices), and if he is from a tribe between whom and you there is a convenant, the blood-money should be paid to his people along with the freeing of a believing slave; but he who cannot find (a slave) should fast for two months successively: a penance from Allah, and Allah is Knowing, Wise.

  2. But whoever has not the means, let him fast for two months successively before they touch each other; then as for him who is not able, let him feed sixty needy ones; that is in order that you may have faith in Allah and His Messenger, and these are Allah's limits, and the unbelievers shall have a painful punishment.