In Genesis 1.26, God created “man” (adam) in his image. Adam here is a plural noun because it refers to a corporate group—humankind. The verse isn’t about two individuals, but about humanity. How do we know this is the case? We know the verse describes all humanity because it specifies that adam is to rule over the whole earth and all the creatures that move along the ground. It’s a mandate that stretches far beyond two individual people and easily applies to all humanity in all of history. The image of God was conferred on the species, not just two individuals.
But that’s not all. Beyond the bare language of the verse, we can see that the verse is also a literary archetype (a typical example; a recurrent theme). What that means is that adam in verse 26 is meant to represent all of humanity through time, performing the roles (subdue, rule) throughout time that God gave to them. While we certainly recognize God as the creator, the primary point of this writing is that humans—both male and female—as the image of God are together given the mandate to fill, rule and subdue the earth.
This is an important continuing point, for humanity being in the image of God has been the primary influence in the world to maintain the value and dignity of human beings. The Bible contains no hint that any harm, either through sin (the Fall) or history, has come to the image of God in humanity, nor is there any suggestion that the image of God has changed in any way in us. Though all have sinned and people have changed, the image of God in us hasn’t changed. Instead of a damaged or lost image being restored, Paul writes in terms of something new happening because of Christ. Again, the image of God in us is neither deficient nor damaged by sin.
In Gn. 1.27, God created “man” (adam) in his image. The verse uses the same plural noun as in verse 26. The verb “create” (barah) speaks not of God manufacturing something, but of God assigning roles and functions. God is bringing functionality to His world in giving a role to the humans. As in v. 26, while Genesis is interested in the historicity of the man and woman, its greater concern is more archetypal than historical—to present them, scripturally, as representatives of all humanity in what God has given them to do and their purpose as humans.
The question must be asked, then: What is the relationship between the image of God and maleness and femaleness? Why has the writer cared to mention that in particular? The point is that they both (the male adam [human] and the female adam [human]) bear the divine image. The text is definitely NOT trying to say that male and female are both needed in partnership to represent the image of God. Gender differentiation has historically never occupied a significant place in the Christian understanding of imago dei, for the reason that if male and female must be present together in order to fully constitute the image of God, then those who are single (including Jesus ) do not reflect the image of God. The fact that male and female are both created in the divine image is intended to convey the value, dominion, and relationality shared by both men and women, but not the idea that the complementarity of the genders is somehow necessary to fully express or embody the divine image.
The thrust of Gn. 1.26-27 is clearly more egalitarian (the equality of male and female) than complementarian (the necessity of both male and female), as if it wants to assure us that Eve, as well as Adam, is in the image of God (she is not some lesser subspecies) and that she, as well as he, is commissioned to rule (responsible care and management; stewardship) and subdue (scientific mandate). The point is that there is no disparity in rank, value, or purpose between them.
Another important point of the text, theologically, is to teach that we as humans (creatures) should be reflecting what God is and does (specifically manage the earth). The Bible is ultimately concerned with the relationship between God and humans, and this chapter, as well as the theme of male/female relationships, bears on the relationships of God with humans, both male and female (lest one think that only men have a right to a relationship with God).
God’s image obviously does not consist in man’s body, since God is without gender, but in his role. Gn. 1 is intensely deliberate in its writing. Its numerology is out the roof. We cannot take the “male and female” of v. 27 lightly, for even in v. 27 itself we find that “male and female” are part of a triple parallelism of expression:
So God created man in his own image
In the image of God he created him
Male and female he created them
Unarguably, humankind is designated by sexual differentiation. Unlike the animals, though, of which the text merely says “after their kind…”, here we read “male and female.” Again, the point is egalitarian and not complementarian, to teach us that they both bear the divine image. Now, this is not to claim they don’t complement each other, for they do, but that is not the point.
We know it is not true that a man needs a woman to be complete, for Jesus was unmarried and celibate, as was already shown. In that same sense we know that marriage between a man and woman is not necessary for Godlikeness. While it is also true that the marriage relationship is designed to reflect the relational model of the Trinity (Eph. 5.21-33), again it is not necessary to do that. It cannot be claimed with any confidence or substance that the differences between male and female represent the differences between YHWH and Jesus in the trinity.
Gn. 1.28: We can also say that humanity’s procreative function is a blessing (Gn. 1.28), not a command. Humans are not commanded to bear children, and the text never hints that only those who bear children are in the image of God or are obeying His mandate. Procreation, instead, is a blessing, and a God-given role of human couples, and is a way that humans can be creators, in a sense as God is, and to bring forth life. (Singleness is not disobedience, nor is celibacy or not having children in a marriage relationship.) We are endowed with the capacity to create life, not the command to do so.
The point of the text is not to establish a biological complementarity
(The idea that God created man and woman to complement each other in the bond of marriage) of the genders.
 When Hebrew wants to pluralize adam in an individual sense it uses bene-Adam (sons of Adam).
 We know that Jesus reflected the image of God: 2 Cor. 4.4; Col. 3.10; 1 Cor. 15.45