Guidelines are here: http://www.rattle.com/poetry/submissions/guidelines/
Info below is copied and pasted from the newsletter:
Issue #45 – Poets of Faith – Deadline: April 15th
Our fall issue will be dedicated to Poets of Faith—and by that we mean poets who are adherents to a specific religious faith tradition. In a slight revision to the guidelines, the poems themselves need not be about faith, so long as the poet qualifies. After reading an early batch of submissions, we realized that your spirituality will be embodied somehow in your poetry, even if that’s not what you’re writing about explicitly, and it’s much more interesting to explore the subtle ways that faith affects the work.
So if you consider yourself a Poet of Faith, see our guidelines page, but the gist is this: Send up to six poems on any subject and a note explaining why you qualify to firstname.lastname@example.org by April 15th.