This is when we first meet Jim Casy who lays down his philosophy in life in an almost preacher-like speech. Casy is talking about his newfound love of people just as they are. He is no longer dividing them into sinners or saved people. He loves them all and wants to encompass them in his existence, showcasing a new religion of the people, expanding beyond the confines of organization and sinking into the chaos that is humanity.
The idea of wrath plays a major role in Steinbeck's novel (as you probably figured out from the title). Steinbeck maintains that as long as the migrant people were angry, they would not break. This anger could turn into action and that action could lead to the power to control their own lives. This quotation marks the mounting wrath of the migrant people and the action that is going to be produced out of it.
This quote is near the end of the novel, as Tom is getting ready to leave. Here Tom captures the spirit of togetherness, creating a line that is both cheesy and effective.