"why should He squander souls?"

In Neil Gaiman’s Sandman, issue #73, “Sunday Mourning,” a character quotes Kipling:

Can anyone tell me the title of the poem this is (presumably) excerpted from? And if you happen to be able to point me toward a website where I could read the complete poem online, that’d be wonderful.

Rudyard Kipling, The Sack of Valhalla

Thank you kindly!