Auguries of Innocence Lines 67-70

Lines 67-70

Every Tear from Every Eye
Becomes a Babe in Eternity.
This is caught by Females bright
And return'd to its own delight.

• These might be the toughest lines yet: it's hard to understand them without knowing anything about Blake's greater vision of reality and mythology. 
• Blake's saying that, whenever you feel real sympathy or sadness and shed a tear, that tear creates something ("Becomes a Babe in Eternity") that, in the spiritual world, will become a reality—the thing you were sad about or felt sympathy for will eventually be made right or fixed: "return'd to its own delight." What we hope for or dream about on planet Earth becomes real in "Eternity." 
• The weirdest part is the bit about how the "Babe" gets "caught by Females bright" before being made into a reality in the eternal world. The "Females bright" are good, mythological figures—like the Graces from Greek Mythology or a more positive version of the Fates. Their job is to keep reality functioning correctly—to make sure that there's joy on the other side of every pain.