v. 17
If the heart turns away, the result is refusing to “hear,” followed by being drawn off course into worship and service of other gods.
v. 18
Moses issues a time-stamped declaration “this day” that the outcome is certain: they will perish and will not prolong their in the they are about to enter by crossing the to possess it.
vv. 17–18 (logic)
The passage forms a cause-and-effect chain: inner turning → refusal to listen → attraction to other worship → loss described as perishing and shortened tenure in the land.