The first two lines mean that a small, beautifully made urn can hold the ashes of great heroes. A large half-acre tomb can also hold the remains of great heroes. Donne uses this image to show that size does not matter. A small urn can honor a person just as much as a huge tomb. This is a metaphor for his love. Even if the world disrespects his love, his love will still be great and meaningful.

The next two lines explain how this will happen. The speaker says that “these hymns” will keep their love alive. It means the poems or sonnets written about their love will keep their love alive. Through these poems, people will understand that he and his beloved loved each other in a pure and holy way. The speaker says their love is so pure that people will “canonize” them. This means their love will become holy. People will pray to learn to love like them.

So, the lovers do not need a big tomb to be remembered. Their love will be remembered through poetry. They will become saints of love because of their pure and holy love.