Those two lines do not rhyme. "Night" does not rhyme with "day." But if you'd gone on to the third line, "Rage, rage against the dying of the light," you would have found "light" rhyming with "night."
However, the poem as a whole--you can find it online, search on "Do not go gentle into that good night"--has a very strict rhyme scheme.
Every one of the nineteen lines either rhymes with the word "night" or the word "day." The scheme is ABA ABA ABA ABA ABA ABAA. The actual rhyming words are:
night/day/light
right/they/night
bright/bay/light
flight/way/night
sight/gay/light
height/pray/night/light
The lines you quoted do contain some "internal rhymes" as noted by Jonathan K.
There is also some "assonance," which means repetition of similar vowel sounds, but not in any regular pattern. When you read it aloud you do hear the similar vowel sounds in "age," "rave," and "day." And then in the next line, "Rage, rage" picks up the sound of "rave."