Whom Jove's great son to her glad husband gave,
Rescu'd from death by force, though pale and faint. (3-4)
The allusion here is to the Greek myth of Alcestis, rescued from the underworld by Hercules as a host-gift for her husband. It's the first in a series of many comparisons, which raises the question: why start with the ancient Greeks?
Mine, as whom wash't from spot of child-bed taint
Purification in the Old Law did save (5-6)
Here's the next simile, which moves from ancient pagan beliefs to early monotheism.
And such, as yet once more I trust to have
Full sight of her in Heaven without restraint. (7-8)
These lines affirm the speaker's belief in the Christian afterlife, concluding the progression from paganism and Judaism that began with the allusion to Alcestis. The speaker's "trust" that he will see his wife again in Heaven is a much stronger word than "hope" or "want." It tells us that he is sure he will see her again, that he fully and truly believes in the Christian afterlife and God's promise of salvation.
Her face was veil'd, yet to my fancied sight,
Love, sweetness, goodness, in her person shin'd
So clear as in no face with more delight. (10-12)
In her "person," the speaker is able to perceive his wife's virtues, rather than her physical features. The seamlessness between his wife's body and soul suggests a Christian idea of heaven as a place in which physical barriers are removed. By contrast, the veil before his wife's face may symbolize the speaker's earthly, un-saved state, which prevents him from totally achieving Heavenly vision.