What does it mean when the Gemara guarantees a person Olam Habah for doing a certain deed (for example saying Ashrei three times a day)? How is it different from any other good deed that one does?
I heard a tape of Rabbi Avigdor Miller once where he says whenever you hear such things there's always a catch (I think he said "fine print"). For example, regarding Ashrei he says it means you live what it says not just recite it.
As to why it is different perhaps because these things encompass most of the Torah.