"To My Dear and Loving Husband" has plenty to say about religion, but it is very discreet and careful about it. The speaker doesn't come right out and say it, but for her, love and religion are very close. The first few lines of the poem, for example, describe love with very subtle references to the Bible. In addition, the last line of the poem talks about love as the key to immortality, to salvation. And remember, Bradstreet lived in a very religious society among Puritans and preachers, so this close relationship between love and religion makes perfect sense.
Many of the things the speaker says about love contain some religious idea or biblical echo, so the poem shows us that many important things in life can be understood through the lens of religion.
Getting to heaven isn't about going to church every Sunday and following other such rules. For Bradstreet, it's about loving people, particularly your family.