Whoe’er she be,
That not impossible she
That shall command my heart and me.

The speaker imagines an as-yet-unknown woman whose power over him will be absolute: whoever she turns out to be, she will not be “impossible” in the sense of unattainable or beyond his reach, because she is destined to “command” both his heart (emotion, desire) and “me” (the whole self, will, identity). The lines dramatize the paradox of love as voluntary surrender—an anticipated submission that feels fated rather than chosen. In Crashaw’s broader poetic world, such language can also hover between earthly courtship and the devotional idiom of being mastered by a higher love, though this excerpt alone does not securely fix the addressee as secular or sacred.