Rav said: The evil inclination is like a fly and sits between the two openings of the heart, as it is said “Dead flies...” And Shmuel said: It is like a wheat [kernel], as it is said “sin crouches at the door (petach).”
On the daf / in context: The two sages give images for the yetzer hara, deriving them from the wording “chatas” and “petach.”
Type of Learning: Image of the yetzer haraWhat Is Learned: The yetzer hara is compared to a fly and to a wheat kernel, emphasizing how small beginnings can become spiritually significant.