Biblical allusions can be seen in quite a few places in Heart of Aztlán. Let's start by looking at the rock. How does Clemente begin his spiritual journey? First, he visits the mystical woman who resides on the edge of town. She tells him "look at the rock," which will be his gateway or portal to his spiritual venture.
The rock might be construed as an illusion to both Exodus 17 and Numbers 20. In Exodus 17, Moses is told to strike the rock to bring forth water that the thirsty people of Israel can drink. In Numbers 20, Moses is told to speak to the rock to bring forth water, so he strikes it.
You might want to discuss how the rock in Aztlán connects to the rock in the Bible.
Another biblical allusion could be the desert Clemente has to wonder through in order to realize his underlying connection with earth and humankind. You might discuss how Clemente's desert travels could be an abridged version of the Israelites' 40 years in the desert.
You also might want to talk about how the character of Crispin could amount to a biblical allusion. He's blind, yet it's Crispin who saves Clemente from the awful storm. In the Bible, blindness is frequently referenced. The blind can sometimes be those who can't see the truth of God and Jesus. Yet sometimes the blind can be those who have a different sort of vision. They have a higher, more prophetic sight.