Elsewhere, I have noted that Adam though not a ‘priest’ in the technical sense (of the Mosaic law) nevertheless functions as a priest in the garden. His dual role was to work the land and take care of it (Gen 2:16). The choice of words here is very significant. In v15, the word ‘work’ (Hebrew ‘avad – ‘serve, till’) was used of cultivating the soil but was also commonly used in a religious sense of serving God (cf Deut 4:19) and of the tabernacle duties of priests (cf Num 3:7-8; 4:23-24, 26, etc). Similarly, to ‘take care of’ the garden (Hebrew shamar – ‘guard, keep’) was used particularly of Levitical responsibilities for guarding the tabernacle from intruders (Numbers 1:53; 3:7-8). These two words are only used in combination elsewhere of the duties of the Levites in the sanctuary. Eden is thus a prototype of later sanctuaries, and Adam is its prototype ‘priest’ with the function of serving God. By working the land and taking care of it Adam also serves God. He is called to look after the sanctuary according to divine instruction just like the later Levitical priests did under Moses. To ignore God’s Word or deviate from it would result in death (eg Gen 12:17; cf Num 3:10).
Priestly responsibility was given first to Adam before Eve was created (Gen 2:15). He acts therefore as a kind of head or representative priest. Eve is conjoined to Adam to assist him in this work as a suitable helper. [Did the Levites who were 'attached to' or 'joined to' Aaron function in a similar way?] The language of “suitable helper” implies that together they functioned together as a ‘priesthood’, yet with differentiated roles.
And so Adam and Eve were more than farmers or gardeners. They had a high calling to serve and guard the sanctuary in which man was made to enjoy fellowship and peace with God. Thus, Adam is a “priest-king” who rules the creation under God’s rule through his obedient service.
One of Adam’s primary priestly responsibilities was to guard the conditions whereby mankind could enjoy abiding friendship with God. This was also the case for the Levitical priests. For Adam it meant keeping God’s one word of command; “You are free to eat from any tree in the garden; 17 but you must not eat from the tree of the knowledge of good and evil, for when you eat of it you will surely die.” (Genesis 2:16b-17).
This is a key verse of the Bible. It describes the great degree of freedom Adam had to enjoy in the wide provisions of the Garden. But it also puts them on probation. If Adam kept (guarded) God’s word, he would also guard the conditions whereby mankind would enjoy abiding friendship with God.
Adam’s role as a priest was thus to guard God’s Word and His moral autonomy. To disobey God’s word was to rob God of his autonomy and declare moral independence. Thus, a biblical priest guards the sanctuary in which he has been placed by guarding the Word of God. Indeed, guarding God’s word must be understood as the primary means of guarding the conditions of lasting friendship with God, since the conditions of lasting friendship with God are always ultimately conveyed through the Word of God (whether spoken or written). If you tamper with his Word you tamper with salvation.
It is notable then that, when Adam failed to guard the sanctuary, their role as primary guardians of the Eden-sanctuary was given to others. God instead placed Cherubim (human-headed winged lions) on the East side of the garden to guard the way back to the tree of life. These cherubim were later depicted on the walls of the temple and a large pair of Cherubim guarded the Most Holy Place of the temple.