The people come with nets to fish for potatoes in the river, and the guards hold them back; they come in rattling cars to get the dumped oranges, but the kerosene is sprayed. And they stand still and watch the potatoes float by, listen to the screaming pigs being killed in a ditch and covered with quick-lime, watch the mountains of oranges slop down to a putrefying ooze; and in the eyes of the people there is the failure; and in the eyes of the hungry there is a growing wrath. In the souls of the people the grapes of wrath are filling and growing heavy, growing heavy for the vintage.

– John Steinbeck

The Grapes of Wrath, Chapter 25. The chapter’s final words are Biblical in tone expressing almost a sentiment of doom. The last sentence references the song Battle Hymn of the Republic written by Julia Howe shortly before the American Civil War. The novel’s title is taken from a line of the song: "Mine eyes hath seen the glory of the coming of the Lord; He is trampling out the vintage where the grapes of wrath are stored; He hath loosed the fateful lightning of His terrible swift sword; His truth is marching on." The "grapes of wrath" metaphor is also an allusion to Revelations 14:19 where evil people perish: "And the angel thrust in his sickle into the earth, and gathered the vine of the earth, and cast it into the great wine press of the wrath of God. And the winepress was trodden without the city, and blood came out of the wine press, even unto the horse bridles, by the space of a thousand and six hundred furlongs." A number of themes are in play in this important passage from the novel. They include the inhumanity of the large farmers, their greed, the anger of the people and the hunger that drives that anger. Steinbeck warns of the rising wrath of people left to starve in a California rich with food destroyed because harvesting isn’t profitable enough. There is foreshadowing of a rebellion by the people against this cruel system. Personification is used by the author in his depiction of the pigs "screaming."