One example of Rukmani's reference to her stone god and goddess in the temple can be seen in the moment of severe drought just after two of her sons start working in the tannery. In chapter 13, Rukmani narrates in first person that when she still saw the "cruel sky" as being "calm, blue, indifferent to our need" she brought a pumpkin and some grains of rice as an offering to her goddess and "wept at her feet," but still the drought did not break (p. 39).
Due to examples like the above, it's evident that faith is a major theme in the book. It's further evident that author Kamala Markandaya wants to demonstrate exactly how significant a role faith in religion plays in lives of peasants in India's villages, just like as we see in her characters' lives. However, what's also important is the fact that Markandaya also portrays her characters' prayers to gods and goddesses as having no effect. Instead, her character Rukmani is portrayed as one who endures a great deal of suffering but continues to maintain the hope that life will persist, and by the end of the story, Rukmani does indeed survive her tribulations. Hence, as the editor of the Critical Guide to British Fiction points out, hope is actually a much more dominant theme than faith in religion (eNotes, "Nectar in a Sieve: Themes"). Therefore, it seems Markandaya is using references to religion to both honestly show that religion was important to Indian peasants but also to show that religion may not necessarily solve any problems; instead, hope is the only real thing that helps the oppressed live through another day.