In the book of Genesis, God reveals to us how he created us in his image.
God created man in his own image, in the image of God he created him; male and female he created them.Genesis 1:27
Our God-given gender enables us to image God in a unique way.
Pope Francis reflected on this passage in a general audience in 2015.
[M]an and woman alone are made in the image and likeness of God: the biblical text repeats it three times in two passages (26-27): man and woman are the image and likeness of God. This tells us that it is not man alone who is the image of God or woman alone who is the image of God, but man and woman as a couple who are the image of God. The difference between man and woman is not meant to stand in opposition, or to subordinate, but is for the sake of communion and generation, always in the image and likeness of God.
Only when seen in the light of each other do man and woman see the gift they have been given.
St. John Paul II also reflected on this in a general audience in 1980, which would later be compiled into his Theology of the Body.
The human body, with its sex, and its masculinity and femininity seen in the very mystery of creation, is not only a source of fruitfulness and procreation, as in the whole natural order. It includes right from the beginning the nuptial attribute, that is, the capacity of expressing love, that love in which the person becomes a gift and — by means of this gift — fulfills the meaning of his being and existence. Let us recall here the text of the last Council which declared that man is the only creature in the visible world that God willed “for its own sake.” It then added that man “can fully discover his true self only in a sincere giving of himself” (GS 24).
Our birth gender reveals to us how we can love others and our unique contribution to the world. The difference of the sexes is not meant to be a barrier to love, but a gift, showing us how we can complement each other.
The Catechism of the Catholic Church further affirms that our biological sex is meant to be seen as an image of God.
Everyone, man and woman, should acknowledge and accept his sexual identity …“In creating men ‘male and female,’ God gives man and woman an equal personal dignity.” “Man is a person, man and woman equally so, since both were created in the image and likeness of the personal God.”CCC 2333
Pope Francis believes that part of our problem with accepting our gender is the tension that still exists between the sexes.
I ask myself, if the so-called gender theory is not, at the same time, an expression of frustration and resignation, which seeks to cancel out sexual difference because it no longer knows how to confront it. Yes, we risk taking a step backwards. The removal of difference in fact creates a problem, not a solution. In order to resolve the problems in their relationships, men and women need to speak to one another more, listen to each other more, get to know one another better, love one another more. They must treat each other with respect and cooperate in friendship … The great responsibility of the Church, of all believers, and first of all of believing families, which derives from us, impels people to rediscover the beauty of the creative design that also inscribes the image of God in the alliance between man and woman.
Above all, our biological sex is meant to be a gift given from God, showing us how we are made in the image and likeness of God.