In Chapter 26 Forster describes Margaret’s observations of Henry’s behavior while organizing his son's wedding. He uses a simile to imply Henry’s responses would be no different were he arranging a funeral. Forster then emphasizes this point with an ironic allusion. He describes Henry’s behaviour as:
[...] tact, of a sort—the sort that is as useful as the genuine, and saves even more situations at board-meetings. Henry treated a marriage like a funeral, item by item, never raising his eyes to the whole, and “Death, where is thy sting? Love, where is thy victory?” one would exclaim at the close.
Through this simile, Forster implies Henry Wilcox is so cut off from his emotions that he would approach organizing a funeral in the same way as he approaches this event. The simile highlights the unromantic, step-by-step approach that Henry takes toward planning. His useful faux-“tact” is helpful in board-meetings, but is emotionally numbing when things are hard. This approach reflects the way in which the Wilcox family sees any event they attend, as formal occasions rather than events infused with emotion and significance.
The ironic biblical allusion that the narrator makes at the end is a deliberate misquote for comic effect. The verse from First Corinthians Forster is referring to actually reads “O death, where is thy sting? O grave, where is thy victory?” and alludes to the resurrection of Christ. The narrator’s incorrect allusion to it in Howards End employs verbal irony. Henry Wilcox doesn’t make a distinction between funerals and weddings. The narrator swaps out “grave” for “love” when they say “Death, where is thy sting? Love, where is thy victory?” By replacing “grave” with “love” when imagining what a guest might say about Henry’s attitude, Forster implies that “love” and “grave” would be the same to him.