4:7 crouching at the door. The Hebrew suggests a threatening demon crouching outside the door of a house. Perhaps there is also an allusion to the serpent lying in wait to strike the heel (3:15; cf. 1 Pet. 5:8).
desire. See note 3:16.
rule over it. Knowing Cain’s heart, God warns him not to submit to the murderous temptation of the devil (cf. 1 John 3:12). Although unregenerate humans can rule over the ground and flocks, they cannot finally master sin (1:26 note; Ps. 53:3; Rom. 8:7).