Couch (verb): rabhats, "to crouch," "lurk," as a beast in readiness to spring on its prey. "If thou doest not well, sin coucheth at the door" (Ge 4:7, the King James Version "lieth"), waiting for it to open. Cain is warned to beware of the first temptations to evil, in his case especially a sullen and jealous disposition (compare Dante, Inferno, I, 30). See ABEL; CAIN. The tribe of Judah is compared for its bravery to a recumbent lion or lioness (Ge 49:9; compare Nu 24:9 f); and Issachar to "a strong ass, couching down between the sheepfolds" (Ge 49:14, the King James Version "between two burdens"; compare Jg 5:16). "The deep that coucheth beneath" (De 33:13), probably the springs of water, or possibly, as Driver suggests, "the subterranean deep, pictured as a gigantic monster."
M. O. Evans