The first and the final lines of every stanza ends in "love"

Rhyme scheme of The Canonization is A B B A C C C A A, and it's persistent throughout every stanza.

The first stanza, for example, follows A B B A C C C A A rhyme scheme with the each alphabet representing a rhyme as below:

A: -ove

B: -out

C: -ace

To modern readers, the terminal sound of "love" and, "improve" (or "approve") doesn't seem to rhyme. However,"-ove" during John Donne's time period was pronounced slightly different from modern pronunciation. It was more similar to pronunciation of "-oave," which allowed them to rhyme!