سورة المطففين

The Prophet (peace be upon him and his family): Ibn Abbas (may Allah have mercy on him) says: When the Prophet (peace be upon him and his family) came to Madina, the people of Madina were among those who gave the shortest measure. So Allah the Mighty and Majestic revealed this verse: وَیْلٌ لِلْمُطَفِّفینَ [Woe to the defrauders]. After that, they gave up their short-measuring and observed fairness and justice.

Imam Baqir (peace be upon him): Muhammad ibn Salim narrates from Imam Baqir (peace be upon him): When Allah permitted Muhammad (peace be upon him and his family) to go from Mecca to Madina, He revealed to him the legal punishments (hudud) and the division of inheritance shares, and informed him of the sins by which and for which Allah made the Fire binding upon those who commit them... Concerning measuring He revealed: وَیْلٌ لِلْمُطَفِّفینَ [Woe to the defrauders], and He did not direct "woe" at anyone until He named him a disbeliever. Allah the Mighty and Majestic has said: "So woe to those who disbelieve from the witnessing of a great Day [of Resurrection]!" (Maryam/37)

Imam Sadiq (peace be upon him): Amr ibn Ubayd came to Imam Sadiq (peace be upon him) and recited this verse: "If you avoid the great sins from which you are forbidden." (Nisa/31) He said: "Master, I would like to know the major sins (kaba'ir) from the Qur'an." The Imam (peace be upon him) began to explain them in detail and said: ... "Short-measuring, on the basis of the verse: وَیْلٌ لِلْمُطَفِّفِینَ [Woe to the defrauders]. Associating partners with Allah, on the basis of: إِنَّ اللهَ لا یَغْفِرُ أَنْ یُشْرَکَ بِه [Indeed Allah does not forgive that partners be associated with Him]."

Ali ibn Ibrahim (may Allah have mercy on him): وَیْلٌ لِلْمُطَفِّفِینَ [Woe to the defrauders] — this refers to those who give short measure and short weight.

Imam Sadiq (peace be upon him): O Muhammad (peace be upon him and his family)! Woe to the defrauders! Those who give you less than your khums.