GEN471 The Sages versed in the topic of yirah [i.e., fear/awe of Heaven - AJL] wrote an explanation of the following verse: “Surely, if you improve yourself, you will be forgiven. But if you do not improve yourself, sin rests at the door” [this verse].  In this verse, Hashem informs Kayin of the confined power of the evil inclination. He is restricted in that he may not come “within the house” to tempt man to sin. He may only stand at the entrance to the house, like a poor man at the doorway. This is spoken about in the Talmud (Sukkah 52b).  “First he [the yetzer hara] is called a ‘passerby,’ then he is called a ‘guest,’ then he is called a ‘man’” (see the text there, with Rashi’s commentary).  This is the meaning of “sin rests at the door.” When man hearkens a little bit to the voice of the evil inclination, so that he opens the door for him, the yetzer hara overpowers him to become a guest in his house. This is what the satan showed Plimo through parables and riddles. At first, he appeared to him as a poor man. He stood outside the door, and he called out for Plimo to open it, which we now understand. [See Talmud, Kiddushin 81a for story of Plimo, a righteous man who encounters Satan on Yom Kippur and lets him into his home. - AJL]. OHRYIS 586