Sa`d bin Abu Waqqas (May Allah be pleased with him) reported: We were with the Messenger of Allah (PBUH) when he asked, "Is anyone of you unable to earn a thousand good deeds?'' One of those present asked: "How can one earn thousand good deeds in a day?'' He (PBUH) replied, "By saying: Subhan Allah a hundred times, then one thousand good deeds will be recorded for him or one thousand sins will be blotted out from his record.'' [Muslim]. Commentary: One thousand good deeds in return for saying the word "Subhan-Allah'' is a minimum reward under the promise that says i.e., ten-fold reward would be given for each good deed. The words "Au yuhattu'' is open to disagreement among the religious scholars. Some of them have mentioned it with "Au'' which means one gets one thousand good deeds or a thousand sins are forgiven; while others have mentioned this Hadith with the word "Wa yuhattu'', that is, one is given a thousand virtues and a similar number of sins are pardoned.
