Mistress

In The first stanza of the poem, the poet addresses his brethrens, telling them about his mistress, how beautiful, intelligent and perfect she is.
In The second stanza he compares her to the angels, saying she's from the heavens and an angel indeed, who have come to save him and filled his life with love and romance. He called her the daughter of God (an angel) here we can see his distinctive use of biblical illusion.
The third stanza went further to brag more about the beauty in the mistress eyes, and how beautiful and active, energetic, vivacious she is. he concludes that indeed she came from the heavens.

In The last stanza of the poem, the poet concludes by saying when death finally comes to take his mistress away, he hopes and prays he dies a day sooner before she does, so he wouldn't feel the pain of living a day without her.