The mishnah on Berachos 2a teaches us that according to Chachamim one can say Krias Shema until chatzos ("midnight").
The mishnah proceeds to tell us that anytime Chachamim say a mitzvah can be performed until chatzos, in actuality the mitzvah can really be performed until dawn.
- For example: burning the fats and the limbs, and korbanos that are to be eaten over the course of 1 day...technically are really allowed be performed until dawn.
The mishnah concludes by asking: if that's the case, then why did Chachamim say chatzos?
"כדי להרחיק את האדם מן העבירה"
"In order to distance a person from an aveirah"
Why is omitting Krias Shema grouped with these two as an aveirah? Shouldn't it be considered more of a bittul aseh?