Enemy Human Beings are sons of Adam that remain unreconciled to God the Creator.

God created us to have an intimate and friendly love relationship with Him. Disobedience to His commands ruined that relationship. God made a provision through the sacrifice of his own son, Jesus Christ, to have that relationship and friendship with God restored.

All human beings are born into a condition of enmity with God, because the condition of the first pair (Adam and Eve) gets passed down to us. We are therefore born dead spiritually. This is why we must be born again.

2 Corinthians 5:14-21

[14] For the love of Christ constraineth us; because we thus judge, that if one died for all, then were all dead:
[15] And that he died for all, that they which live should not henceforth live unto themselves, but unto him which died for them, and rose again.
[16] Wherefore henceforth know we no man after the flesh: yea, though we have known Christ after the flesh, yet now henceforth know we him no more.
[17] Therefore if any man be in Christ, he is a new creature: old things are passed away; behold, all things are become new.
[18] And all things are of God, who hath reconciled us to himself by Jesus Christ, and hath given to us the ministry of reconciliation;
[19] To wit, that God was in Christ, reconciling the world unto himself, not imputing their trespasses unto them; and hath committed unto us the word of reconciliation.
[20] Now then we are ambassadors for Christ, as though God did beseech you by us: we pray you in Christ's stead, be ye reconciled to God.
[21] For he hath made him to be sin for us, who knew no sin; that we might be made the righteousness of God in him.

Maintaining submission to God and obedience to God maintains this friendship.

How human beings can renew enmity with God

James 4:1-10

[1] From whence come wars and fightings among you? come they not hence, even of your lusts that war in your members?
[2] Ye lust, and have not: ye kill, and desire to have, and cannot obtain: ye fight and war, yet ye have not, because ye ask not.
[3] Ye ask, and receive not, because ye ask amiss, that ye may consume it upon your lusts.
[4] Ye adulterers and adulteresses, know ye not that the friendship of the world is enmity with God? whosoever therefore will be a friend of the world is the enemy of God.
[5] Do ye think that the scripture saith in vain, The spirit that dwelleth in us lusteth to envy?
[6] But he giveth more grace. Wherefore he saith, God resisteth the proud, but giveth grace unto the humble.
[7] Submit yourselves therefore to God. Resist the devil, and he will flee from you.
[8] Draw nigh to God, and he will draw nigh to you. Cleanse your hands, ye sinners; and purify your hearts, ye double minded.
[9] Be afflicted, and mourn, and weep: let your laughter be turned to mourning, and your joy to heaviness.
[10] Humble yourselves in the sight of the Lord, and he shall lift you up.

There are two spiritual powers that are seeking to influence and control our lives. The legitimate spiritual power is God the Creator the illegitimate spiritual power is the devil or the Satan. By submitting to the one we are resisting the other. Therefore if we are submitted to God we are resisting the devil; on the other hand if we are resisting God we are submitting to the devil.

1 John 2:15-17

[15] Love not the world, neither the things that are in the world. If any man love the world, the love of the Father is not in him.
[16] For all that is in the world, the lust of the flesh, and the lust of the eyes, and the pride of life, is not of the Father, but is of the world.
[17] And the world passeth away, and the lust thereof: but he that doeth the will of God abideth for ever.