Rashi on Genesis 4:7/רש"י על בראשית ד׳:ז׳

1הלא אם תטיב IF THOU MENDEST — Its meaning is as the Targum gives it: “if thou wilt improve thy doings, thou shalt be forgiven”.

2לפתח חטאת רובץ SIN CROUCHETH AT THE ENTRANCE — Right up to the door of your grave (until your death) your sin will be preserved.

3ואליך תשוקתו AND UNTO THEE IS ITS LONGING — The longing of sin; it refers to the evil inclination. This is continually longing and desiring to make you sin.

4ואתה תמשול בו NEVERTHELESS THOU MAYEST RULE OVER IT — If you desire to, you can gain the victory over it (Kiddushin 30b).