“Peacocks often appear in early Christian art as a symbol of the Resurrection and Eternal Life. There are various levels to this symbolism.
Pagan Roots
The most obvious is a carry-over from ancient pagan religions, some of which held the belief that the peacock’s flesh never decayed, even after it died. Early Christians, therefore, adopted the bird as a symbol of the Resurrection, Christ’s eternal, glorious existence.
Medieval Theories
In medieval times, it was also thought that peacocks molt (shed their feathers) every year, and the new ones that grow are more beautiful than the old ones. Along with this idea, medieval legends included the theory that the gorgeous colors of a peacock’s feathers came from a special diet: It was believed that peacocks could kill and eat poisonous serpents, ingesting the poison and transforming it into the colors of their feathers. This too contributed to their being an apt symbol of Christ’s Resurrection, since Christ “became sin” [cf 2 Corinthians 5:21] for us on the Cross, but then rose from the dead with his glorified body and wounds having conquered the powers of evil.
Regardless of the biological accuracy or inaccuracy of these traditions, they help explain why Christian artists often used peacocks as a symbol of the Resurrection and Eternal Life.
Hidden Splendor
Personally, however, I have always been moved even more deeply by another level of symbolism that we can discover in this intriguing bird.
During the normal activities of a normal day, peacocks are fairly normal looking animals. And yet, all the while they are pecking and clucking like your average fowl, a hidden splendor lies underneath. When they spread their tail-feathers, this magnificence shines forth, revealing their true beauty.
The symbolism here is clear. When you see a Christian walking along the street, you can’t tell the difference between him and someone who has never been baptized. From all external appearances, they are both just human beings making their way through the hustle and bustle of daily life. And yet, underneath that ordinary appearance, the Christian soul enjoys a hidden splendor through the transforming power of God’s grace. The Blessed Trinity actually dwells in the soul who lives in that grace. And the person living the life of grace has also received a plethora of spiritual gifts: the theological virtues and the other infused virtues; the gifts of the Holy Spirit; the sacramental seals coming from baptism and confirmation, etc.
These spiritual realities are habitually and dynamically present in every Christian who lives the life of grace, but they are not visible in the ordinary way. Their full splendor will only become visible when the Christian enters into eternal life and comes to share in Christ’s own glorious resurrection. At that point, the hidden magnificence of each Christian’s soul will be revealed, to the wonderment of all, similar to a sudden spreading of the peacock’s magnificent feathers.
It’s only an artistic symbol, so there isn’t a perfect correlation. But it’s a lovely one, in my opinion.”
Summa Catechetica, "Neque enim quaero intelligere ut credam, sed credo ut intelligam." – St Anselm, "“Si comprehendus, non est Deus.” -St Augustine, "Let your religion be less of a theory, and more of a love affair." -G.K. Chesterton, “When we pray we speak to God; but when we read, God speaks to us.” -St Jerome, "As the reading of bad books fills the mind with worldly and poisonous sentiments; so, on the other hand, the reading of pious works fills the soul with holy thoughts and good desires." -St. Alphonsus Liguori, "And above all, be on your guard not to want to get anything done by force, because God has given free will to everyone and wants to force no one, but only proposes, invites and counsels." –St. Angela Merici, “Yet such are the pity and compassion of this Lord of ours, so desirous is He that we should seek Him and enjoy His company, that in one way or another He never ceases calling us to Him . . . God here speaks to souls through words uttered by pious people, by sermons or good books, and in many other such ways.” —St. Teresa of Avila, "I want a laity, not arrogant, not rash in speech, not disputatious, but men and women who know their religion, who enter into it, who know just where they stand, who know what they hold and what they do not, and who know their creed so well that they can give an account of it, who know so much of history that they can defend it. I want an intelligent, well-instructed laity… I wish you to enlarge your knowledge, to cultivate your reason, to get an insight into the relation of truth to truth, to learn to view things as they are, to understand how faith and reason stand to each other, what are the bases and principles of Catholicism, and where lie the main inconsistences and absurdities of the Protestant theory.” (St. John Henry Newman, “Duties of Catholics Towards the Protestant View,” Lectures on the Present Position of Catholics in England), "We cannot always have access to a spiritual Father for counsel in our actions and in our doubts, but reading will abundantly supply his place by giving us directions to escape the illusions of the devil and of our own self-love, and at the same time to submit to the divine will.” —St. Alphonsus Ligouri, "The harm that comes to souls from the lack of reading holy books makes me shudder . . . What power spiritual reading has to lead to a change of course, and to make even worldly people enter into the way of perfection." –St. Padre Pio, "Screens may grab our attention, but books change our lives!" – Word on Fire, "Reading has made many saints!" -St Josemaría Escrivá, "Do you pray? You speak to the Bridegroom. Do you read? He speaks to you." —St. Jerome, from his Letter 22 to Eustochium, "Encounter, not confrontation; attraction, not promotion; dialogue, not debate." -cf Pope Francis, "God here speaks to souls through…good books“ – St Teresa of Avila, Interior Castle, "You will not see anyone who is really striving after his advancement who is not given to spiritual reading. And as to him who neglects it, the fact will soon be observed by his progress.” -St Athanasius, "To convert someone, go and take them by the hand and guide them." -St Thomas Aquinas, OP. 1 saint ruins ALL the cynicism in Hell & on Earth. “When we pray we talk to God; when we read God talks to us…All spiritual growth comes from reading and reflection.” -St Isidore of Seville, “Also in some meditations today I earnestly asked our Lord to watch over my compositions that they might do me no harm through the enmity or imprudence of any man or my own; that He would have them as His own and employ or not employ them as He should see fit. And this I believe is heard.” -GM Hopkins, SJ, "Only God knows the good that can come about by reading one good Catholic book." — St. John Bosco, "Why don't you try explaining it to them?" – cf St Peter Canisius, SJ, Doctor of the Church, Doctor of the Catechism, "Already I was coming to appreciate that often apologetics consists of offering theological eye glasses of varying prescriptions to an inquirer. Only one prescription will give him clear sight; all the others will give him at best indistinct sight. What you want him to see—some particular truth of the Faith—will remain fuzzy to him until you come across theological eye glasses that precisely compensate for his particular defect of vision." -Karl Keating, "The more perfectly we know God, the more perfectly we love Him." -St Thomas Aquinas, OP, ST, I-II,67,6 ad 3, “But always when I was without a book, my soul would at once become disturbed, and my thoughts wandered." —St. Teresa of Avila, "Let those who think I have said too little and those who think I have said too much, forgive me; and let those who think I have said just enough thank God with me." –St. Augustine, "Without good books and spiritual reading, it will be morally impossible to save our souls." —St. Alphonsus Liguori "Never read books you aren't sure about. . . even supposing that these bad books are very well written from a literary point of view. Let me ask you this: Would you drink something you knew was poisoned just because it was offered to you in a golden cup?" -St. John Bosco " To teach in order to lead others to faith is the task of every preacher and of each believer." —St. Thomas Aquinas, OP. "Prayer purifies us, reading instructs us. Both are good when both are possible. Otherwise, prayer is better than reading." –St. Isidore of Seville “The aid of spiritual books is for you a necessity.… You, who are in the midst of battle, must protect yourself with the buckler of holy thoughts drawn from good books.” -St. John Chrysostom