James Joyce, along with other modernist writers such as Virginia Woolf, often used the technique of "ephiphany" in which their characters have a moment of clarity, seeing into the heart of a matter--a flash of insight that explains something about existence. Such is what happens to the young boy in "Araby," which is essentially a bildungsroman. In going to the bazaar to bring a gift to the girl he has idealized as holy and pure, he learns that it is a place of sexuality and materialism rather than spirituality. He realizes his own vanity, i.e., the futility of life in Dublin, his own worthlessness, his own foolishness, his unprofitable use of time, and the ridiculous high opinion he has of himself. See eNotes for definitions of ephiphany and bildungsroman.
The religious imagery in Araby seems to be focused on Mangan's sister. The protagonist identifies her figure “by the light from the half-opened door.'' The way she is lit from behind causes her to have an unearthly glow, which he associates immediately with some heavenly body, possibly even an angel. Symbolically the Catholic priest, a former tenant of the narrator's house, may be considered to represent the entire Catholic church, and thus, by extension, books left by the priest may represent the protagonist’s own feelings of ambiguity toward religion, especially towards Catholicism. Returning to Mangan's sister, the protagonist views her as a “symbol of purity and feminine perfection.” I’m sure this seems sketchy in such short space; however, follow the link below to learn more about the specifics of this religious imagery and the meaning behind the protagonist's destination, as well as more about the varying imagery within the story.
The destination of Araby's protagonist signifies two things: the symbol of his idealization and the truth of his coming of age. This boy has idealized Mangan's sister and his feelings toward her. He has misinterpreted his religious teachings at school and has turned his lust into a spiritual devotion. In the same way, the bazaar, a church sponsored event, is not the religious affair it claims to be. Like the boy's lust, it simply panders to a base human and animalistic instinct, greed in both the sellers and buyers of trinkets. When the boy sees this, particularly in overhearing the conversation between the adult men and women, he understands how he has foolishly misunderstood himself and the world.
The religious imagery appears in the portrayal of setting and character. Mangan's sister is the boy's image of the Virgin Mary, pure and chaste and worthy of devotion. The boy himself is a devout follower, a wise man if you will, who must spend his time in the priest's room, devoting himself to thoughts of her. He also, like a wise man, goes to get a gift for her, a token of his devotion - although his experience at the bazaar so disillusions him that he leaves without making a purchase. The use of the priest's antechamber and the description the narrator gives of his object and his "love" are reinforcements of religious imagery.