This event occurs in Chapter 12 of the novel. Reverend Sykes announces that the church offering for the week that Scout and Jem are visiting and for the following weeks will go to Helen "to help her out at home." Tom is the sole breadwinner in his home; so even though Atticus is defending Tom free of charge, Tom has been imprisoned since his arrest and is, therefore, not able to make money to support his family's daily needs.
Helen Robinson does eventually go to work for her husband's former employer Link Deas, but at the time that the church collects money, charitable donations were the only source of money and supplies that the Robinsons had.
Harper Lee uses incidents such as the announcement about the collection money to highlight the generosity of Calpurnia's church toward a local resident and to contrast that charitable spirit with the hypocrisy of some of Maycomb's other residents, such as the ladies who attend Aunt Alexandra's missionary tea.
Scout and Jem visit First Purchase African M.E. Church with Calpurnia in Chapter 12 of To Kill a Mockingbird. While there, it is announced that a special collection will be taken for Helen Robinson, who is Tom's wife. This collection of money is "to help her out at home." After the collection is taken, Reverend Sykes tells his congregation that they do not have enough money yet. He then explains that Helen has children at home. She cannot leave them home alone so that she can work. She has no income because her husband is in jail. Reverend Sykes then has the doors to the church closed until enough money is given to equal ten dollars. He asks for the congregants who do not have children to contribute extra. Eventually, enough money is collected for Helen.
Scout soon finds out more details of Helen's situation. Her husband has been accused of a crime against a white woman and this has made it difficult for her to even find work. Calpurnia tells Scout that people do not want to associate with Tom's family.