Adam’s priestly role in the Garden of Eden is apparent both because the Garden served as an earthly sanctuary, and because Adam and Eve did the work of priests. And just as the Garden of Eden was a precursor of the tabernacle and temple, Adam and Eve were precursors of the priests that ministered in those sacred buildings. In Genesis 2:15, we read:

The Lord God took the man and put him in the Garden of Eden to work it and to take care of it.

The Hebrew verbs avad, meaning “work,” and shamar, here translated “take care,” are both rather common and can mean many things. But together they form a technical phrase describing priestly work. For example, in Numbers 3:8, we read:

[The Levites] are to take care of all the furnishings of the Tent of Meeting, fulfilling the obligations of the Israelites by doing the work of the tabernacle.

In the creation account, Adam and Eve are created in God’s image not only to rule and subdue, but also to represent. They are supposed to, just like the priestly role in Israel — the priests were representations or go-betweens, mediums, between God and mankind — so Adam and Eve are made to do the exact same thing. They are to rule, to serve, to obey, and thus represent God on earth, not only to rule like him, but also to show what he is like, which is the primary role of a priest. [Prof. Jeffrey A. Volkmer]

God’s covenant with Adam was, and still is, binding on all humanity. So, humanity is still responsible to God for fulfilling the moral obligations that flow from these priestly duties. For example, we’re all called to serve God and worship him, to cultivate and guard the creation, and to turn the whole world into a sanctuary that’s fitting for God’s presence. And in the church, God has given us additional obligations, such as rendering sacrifices of praise and obedience to him and proclaiming his goodness to the world. As Peter told the church in 1 Peter 2:5, 9:

You … are being built into a spiritual house to be a holy priesthood, offering spiritual sacrifices … [Y]ou are a chosen people, a royal priesthood, a holy nation, a people belonging to God, that you may declare the praises of him who called you out of darkness into his wonderful light.