What is the state of holiness in which God created the first humans?

Answer 1

The word is "perfect". When originally created everything, and this includes Adam and Eve, was 'very good' : Gen 1:31 And God saw every thing that he had made, and, behold, it wasvery good. And the evening and the morning were the sixth day.

This was before Adam and Eve had sinned. Afterthey sinned and sin entered the world, God came as Jesus Christ and offered Himself as a sacrifice for all sin:-

Heb 10:17-18 KJV And their sins and iniquities will I remember no more. [v. 18] Now where remission of these is, there isno more offering for sin.

This means God a person's sins will not be remembered by God:-

Heb 10:16-17 This is the covenant that I will make with them after those days, saith the Lord, I will put my laws into their hearts, and in their minds will I write them; [v.17] And their sins and iniquities will I remember no more.

This therefore makes sinful men consecrated, or 'set apart as holy' [Oxford Dictionary]:-

Heb 10:19-20 [v. 19] Having therefore, brethren,boldness to enter into theholiest by the blood of Jesus, [v. 20] By a new and living way, which he hath consecrated for us, through ... his flesh;

If sinful man can become holy, this means that a sinless person such as Adam and Eve were before they sinned must already have been holy, and this means they would have been perfect:-

Heb 10:14 For by one offering he hath perfected for ever them that are sanctified.

Answer 2

Jewish answer:

According to Jewish tradition, God created Adam and Eve (Chava) on a high level of holiness. They were prophets, able to walk with God and stand in His presence. This high level lasted only until they disobeyed God's command (Genesis ch.3), but they lived out the rest of their lives in piety, repentance and the service of God.