The title of "The Canonization" by John Donne is a key to understanding the poem's message concerning love and poetry. According to the Merriam-Webster Dictionary, to canonize is "to declare [a deceased person] an officially recognized saint." At the end of the fourth stanza, the poet declares himself and his lover "canonized for love." Since they are nobody special in terms of fame or power, when they die they will not merit "tombs and hearse" or "piece of chronicle" (that is, mention in a history book). Instead, they will be memorialized in love poems. The "legend" of their love will be "fit for verse." "Pretty rooms" will be built for them in love sonnets. People will deem them saints and, as implied in the fifth stanza, "invoke" or pray to them and see their love as an ideal pattern to follow.
Beginning in the first stanza, the poet makes it clear that love is the most important thing to him. He declares to his listeners that they can insult his illnesses, age, or poverty, or they can go do something else such as study, find a home, or observe the king, as long as they let the poet love.
The second stanza emphasizes that the poet's love harms nobody. It does not sink ships or cause disasters or illnesses. Just as soldiers fight wars and lawyers argue in courts, the poet wants to be free to pursue his love.
In the third stanza, the poet points out that the love he and his lover share gives them great power. They are like the mythic phoenix, which can "die and rise" because of their mysterious love.
We see, then, that the poet's love is of supreme importance to him, it harms no one else, and it gives him and his lover ability to overcome even death. Instead of being remembered by material monuments, their love will be immortalized through poetry. People who read the poems will approve of their love, consider them saintly, and invoke them so that they also might find similar love.