The answer to why priests must be men is based in Sacred Scripture.
The first human being that God created was a male named “Adam”. From Adam’s substance, God made Eve as a gift to Adam to be his friend, and helper in his work of tending and protecting God’s Garden. Furthermore, Eve was formed by God to be the wife of Adam; and thus God provided the man and his wife the capacity to become one flesh. The one-flesh union between the man and his wife is for the sole purposes of producing greater intimacy between the married couple, as well as conceiving children of God. Therefore, the capacity to become one flesh provides the man and his wife the God-given means to be obedient to God’s command to be fruitful and multiply.
Then the fall of mankind occurred. In the fall Eve was deceived by Satan into thinking that, through her own doing, she could become more like God, and thus she fell for the temptation Satan was presenting her. And Adam, fully knowing better, nevertheless stood silently by and listened to that whole mess go down. Adam was not deceived, but rebelled against the authority of God and, for his own reasons, intentionally went along with Eve into partnership with Satan. Because of this original sin by both of them, they got kicked out of the Garden of Eden by God. Only perfection could live in the Garden, and Adam and Eve, having sinned against God, were no longer perfect.
After some centuries had passed, God chose to form a people through Abram, and continued to prophesize through them and to them that a savior of the world, a messiah, was coming. And when the time was right God the Father sent His only Son to be born unto the world through the Virgin Mary. Holy Mary, mother of God, full of grace, named the messiah, “Jesus”.
That incarnate Son of God, Jesus, remains without sin: He is perfect. And although He never sinned, He was crucified for saying He was God. He is God, and in spite of that, He emptied Himself of His glory and suffered and died for our sin, including the original sin of Adam and Eve. The good news is that Jesus resurrected from the dead and walked on Earth again before ascending into heaven.
Thus Jesus is the new Adam: the first born of His new creation. Unlike the first Adam, the new Adam came with no intention of silently standing by and watching His Father’s old creation become further desecrated. Jesus came to speak and to do -to puff life, love and light back into a hell-bent world.
Jesus instituted His Bride -His one, holy, catholic and apostolic Church- to partner with Him and carry on His salvic mission. To do this He chose 12 men as His initial apostles, and instituted His seven sacraments through them. Men have continued His work of tending and protecting His new Garden by passing on His teachings and traditions through the Sacrament of Holy Orders. Then the priests/bishops continue to offer the Sacraments to God’s children so that they too may becoming one flesh with their Bridegroom, Jesus.
Why men? Because Jesus Christ was, very specifically, the incarnate Son of God: very specifically Jesus Christ was born a man. As a man Jesus is the head of the Body of Christ -His one, holy, catholic and apostolic Church- as well as the bridegroom of the Bride of Christ -also His same Church.
Thus, since Jesus is a man, and as a man He is the new Adam, it is men’s cross to bear to undo the residual effects of the sin of the first man, Adam.
Specifically, men of the Bride of Christ participate in this undoing through submitting to the call of Jesus to come tend and protect His new Garden with Him through the leading of prayers, the teaching of the faith, and the listening to and counseling of the Bride of Christ.
And also, very specifically, the priests/bishops act in the persona Christi as they participate in their relationships with God the Father, the bridegroom of Christ, and the brotherhood of Jesus. In the persona Christi the priests/bishops undo the silence, rebellious acedia, and unloving heart that the first Adam demonstrated towards God through his behavior towards his wife, Eve. In the persona Christi the priests/bishops reconcile God’s faithful and chosen people back to God and God’s perfect Garden (heaven) by speaking and doing the Sacramental rites and liturgies. In this way God’s kingdom is multiplied as the fruitfulness of the Bride’s one-flesh union with Christ is proven true.
As their act of reparation for the residual effect of Adam the priests/bishops must speak and do the three Sacraments of Initiation to this many people: “Look up at the sky and count the stars, if you can. Just so…shall your descendants be” (Gen: 15:5). When the full number of gentiles has come into Jesus’ Church, Jesus returns for His Bride and Satan’s playtime on Earth is basically over (Rom. 11:25-26).
All of God’s people are called by God to be holy as He is holy, and therefore to spread His healing balm of loving forgiveness on the world.
But: God first gave Adam the command to not eat of the tree of the knowledge of good and evil. Then God made Eve (Gen. 2:15-25). Satan knew Eve had obtained her information second hand (contrast Gen: 2:16-17 with Gen. 3:3). So who did Satan approach? Satan approached Eve: Satan led Eve to doubt what Adam had told her, for Satan asked her, “Did God really say that?”
Eve coveted the pretty created thing that Satan held out for her to see -it looked so good to her! She knew God is good, and so being like a god must be good too, right? Eve was tricked by Satan into thinking she could become more like God under her own individual and human power, in fact, it seemed to her that if she followed her (twisted, deceived) thinking she could actually become a god. Because Eve only knew one God, she was deceived into thinking that being “like gods” meant that she would become more like the one true loving God -how bad could that be? That is to say that Eve apparently did not understand the difference between the meaning of the words “God” and “god”; “God knows well that the moment you eat of it your eyes will be opened and you will be like gods who know what is good and what is bad” (Gen 3:5).
But in her confusion, why did Eve not consult her husband, who had spoken directly with God, and was actually with her when Satan was speaking to her? How horribly disrespectful was that to not submit to the authority of her husband and humbly consult him, the one she was given to!!
If men must participate with Jesus to undo the silence, rebellious acedia and unloving actions of the first Adam through, very specifically, the speaking and acting of the rites of the seven Sacraments and the liturgy, how must women participate with Jesus and what must women undo? The cross that women bear is to undo the residual effects of the sin of Eve.
Eve was disrespectful to her husband, and disobedient to God. But Jesus gave women a role-model in His mother, Mary: Mary is thus the mother of God. And because Jesus has a body in the Bride of Christ, Mary is also the mother of His one, holy, catholic and apostolic Church. In her “Yes” to bearing and rearing God’s son, Mary picked up the cross as the new Eve and showed the women of the world how to live full of wonder within God-given relational boundaries and joyfully submit to God-given authorities. And in that way women are friends and helpers in the Garden of the new Adam through their husbands as well as through their priests/bishops: women bear biological children and rear spiritual children for the Kingdom of God. Thus a woman is “saved through childbearing, provided she continues in faith and love and holiness -her chastity being taken for granted” (1Tim. 2:15).
Thus, allowing for female priests would be an act of denying God’s theology of the Body, which would default to an approval of the relationships of female father and female husband and female brother: in violation of the sacramental plan of salvation that the Lord has decreed.
“Defer to one another out of reverence for Christ. Wives should be submissive to their husbands as if to the Lord because the husband is head of his wife just as Christ is head of His body the Church, as well as its savior. As the Church submits to Christ, so wives should submit to their husbands in everything.
Husbands, love your wives, as Christ loved the Church. He gave himself up for Her to make Her holy, purifying Her in the bath of water by the power of the word, to present to Himself a glorious Church, holy and immaculate, without stain or wrinkle or anything of that sort.
Husbands should love their wives as they do their own bodies. He who loves his wife loves himself. Observe that no one ever hates his own flesh; no, he nourishes it and takes care of it as Christ cares for the Church -for we are members of His Body: ‘For this reason a man shall leave his father and mother, and shall cling to his wife, and the two shall be made into one.’ This is a great foreshadowing; I mean that it refers to Christ and the Church.
In any case, each one should love his wife as he loves himself, the wife for her part showing respect for her husband” (Eph. 5:21-33).
Women are not God, nor are they female fathers or husbands or brothers, but in the abundance of God’s mercy He has given both males and females a head in a God-man in whom all of humanity is invited to become one -Jesus Christ.
Through the Sacrament of Baptism God places you in Christ. Then through the Sacrament of Communion God places Christ in you. Then finally through the Sacrament of Confirmation you do not become “like gods”, which was the desire of Eve, but you actually become one with the Son of God, Jesus Christ, through the unifying action of your indwelled Holy Spirit. And then in heaven this union of the Bridegroom and Bride is consummated through the glorification of Jesus’ one Body.
Besides explaining why priests must be men, this writing also explains how Satan increases his playtime on Earth by slowing down the filling of God’s Church through effecting his three primary targets of human sexuality, the sacraments and the priesthood.
But no worries: God is only good. In the end the Bridegroom will “tread out in the winepress the blazing wrath of God the Almighty” (Rev. 19:15), and “the devil who led them astray was hurled into the pool of burning sulphur, where the beast and the false prophet had also been thrown. There they will be tortured day and night, forever and ever” (Rev. 20:10).