Shoot, swd, I'm giving up. I googled "Death is not extinguishing the light" and found many promising hits; but nothing was obvious. I even found a site where you could search his poems by first lines, and...no matches. So maybe it's not from a poem? There are plenty of pages of quotations, but that won't answer your question. [frustration e]

I tried Bibliomania, but they don't have Tagore listed.

A long shot--you might try Amazon.com and bring up books by him--you might just see this as a "sample of what's inside".