Allah swears an oath by the self-reproaching soul. The soul that is kicking itself for the wrongs that it has done. This deep guilt is enough of a proof for the Day of Judgement.
Guilt isn't something that is taught. People feel it naturally because Allah has instilled this moral alarm system within us that lets us know when we've done something wrong and that there should be consequences (whether we face them or not in this life). Many times, ...