Eliot uses many allusions in "The Burial of the Dead," and using them allows him to connect his writing and his commentary on the dismal nature of modern society to human history.
For instance, in the very beginning, with the line "April is the cruelest month," he alludes to the writer Geoffrey Chaucer, who suggested that April is a time of rebirth in The Canterbury Tales. By immediately opposing this point of view, Eliot shows how society has changed and grown more cruel and dark. Eliot also alludes to Dante Alighieri's Inferno when he writes,
Speak, and my eyes failed, I was neither
Living nor dead, and I knew nothing ...
These lines allude to the line from Dante's Inferno in which Dante states that all speech failed him and that he "did not die" but did not remain alive.
Eliot also alludes to John Webster's play The White Devil when he writes,
Oh keep the Dog far hence, that's friend to men,
Of with his nails he'll dig it up again!
This line is quite similar to Webster's line
But keep the wolf far thence, that's foe to men
For with his nails he'll dig them up again.
This is one of many lines in which Eliot slightly changes the words of other prominent writers to underscore the symbolic nature of his commentary.