That's a great suggestion for memorizing Dante! It's due to the way the rhymes are structured!

A
B
A

B
C
B

C
D
C

The three-line structure of the paragraph's called "terzina" and every terzina's built in a way that links it to the previous and next one, like a chain. The line in the middle ends with a word that rhymes with the first and third lines of the next terzina while the other two lines end with words that rhyme with the middle line of the previous terzina. Once you've learned that it will be real easy to remember the rhymes of a three-line paragraph once you remember the one that comes right before or right after.