And you, my father, there on the sad height, Curse, bless, me now with your fierce tears, I pray. Do not go gentle into that good night. Rage, rage against the dying of the light.
In the last lines of the poem, the speaker turns to addressing his father. His father is on the verge of death, which the speaker describes as a "sad height."
We think this is probably an allusion to looking down into the Biblical valley of death; the metaphorical mountain where the father stands is the edge of the mortal world.
The speaker begs his father to cry passionately, which will be both a blessing and a curse. After all, the father's death is heartbreaking. But if he battles against the odds, it might also be heroic.
The speaker ends with the two lines that are repeated throughout the poem, asking or instructing his father not to submit to death – instead, he should rant and rave and fight it every step of the way.