In Aelfric of Eynsham’s homily, “On the Greater Litany” (“In Letania Maiore”), he also draws from St. Augustine’s egg material when quoting Lk. 11:12.
“God is our Father through his mildheartedness [ie, mercy]. And the fish betokens faith, and the egg, holy hope; and the loaf, true love.
“God gives these three things to His chosen, for no man can have God’s kingdom unless he has these three things. He must believe rightly, and have hope in God, and have true love for God and men, if he would come to God’s kingdom.
“…The egg betokens hope. For the birds do not propagate like other animals, but first give birth to an egg; and then, with hope, the mother raises that egg to be a bird. In like manner, our hope does not yet come to what it hopes for, but is like an egg. When it gets what it has been promised, it will be a bird.”
This translation is adapted from The Homilies of the Anglo-Saxon Church, Vol. 1: The Sermones Catholici, or Homilies of Aelfric, by Benjamin Thorpe.