"I consider the blessing of a wife as most justly described in those discreet lines of the poet, 'Heaven's last best gift.'"

 A quotation from Paradise Lost by John Milton (1608-1674):

Her hand soft touching, whispered thus: Awake
My fairest, my espoused, my latest found
Heaven's last best gift, my ever new delight.

(Book 5. 1. 18-20)