Crashaw uses many religious themes in his poems. From his three poems: "To the Infant Martyrs", "I am the Door" and "On the Wounds of Our Crucified Lord" we can learn what few of those themes are.

As mentioned, all of those themes are connected to religion. The most obvious one is the crucifixion and the life of Christ. In these specific poems we can also see the themes of Christ's body parts as metaphors, the concept of outcome to every deed and the idea of repayment for virtuous actions. I will focus on the last theme - the idea of repayment for virtuous actions.

In his poem, "To the Infant Martyrs", Crashaw describes the journey that the souls of the murdered babies go through on their way to heaven. Once the souls break from their "new built cages" (1) - their bodies, they begin to transcend to heaven...