From these verses it is easily gathered that the Christian view of the Old Testament. The Old Testament is presented as the only foundation of the New Testament. If we were to remove the Old Testament, it would be like removing the walls from a building – the roof with instantly fall to the ground. From the Old Testament scriptures one finds the only logical path to faith in Christ, and so it is profitable for doctrine, for reproof, for correction, for instruction in righteousness.
To ask how the Old Testament is profitable is not different than asking how the scriptures, Old or New are profitable. A proper answer could easily be well over a thousand page book. However to summarize at a high level and to remove any conflict with those aspects of the Old Covenant that were superseded by there fulfillment in the New, possibly this would suffice.
The Old Testament presents founding ideas upon which Christianity would otherwise have no meaning:
- Establishment of the single God who created the universe and to whom
we owe all our obedience to.
- Establishment of Adam’s first sin, from
which the curse and threatening of the covenant of works was exacted
upon humanity establishing the natural condemned depravity of man.
- Establishment of a clear moral law of loving God and our neighbor,
upon which any honest person would be convicted of sin.
- Upon these grounds, promising a Messiah to take upon himself the vindictive
justice of God’s law for the penalty of sin, in order to redeem a chosen people.
- To establish a literal people, separate from the
world, called to obey special ceremonies, civil rules and true
holiness, as representatives of God’s overall design of salvation for
the world; his threatening for sin and prophesies of redemption.
- To provide prophets, especially when the truth deposited to Israel was
nearly collapsing under the weight of national sins, in order to
remind God’s people and the world of man’s absolute inability to live
up to these rules and that they might more eagerly put their hopes in
the expected Messiah.
When all these things are combined, I would summarize the entire Old Testament scriptures are the best means to smash self righteousness and to leave oneself in utter desperate fear of eternal wrath, in order that we would flee to Christ for salvation, having full hope that God will completely save any who come to him by faith.
Naturally all of this is profitable for doctrine, for reproof, for correction, for instruction in righteousness, etc. Regarding the tearing down of the wall of partition this is only like the transformation of caterpillar to butterfly. Everything comes from the one and fills out the old in an unexpected way. The ceremonies turned out to be symbols and shadows of Christ's atonement for sin (Heb 10:1). The moral laws, written on stone, became a living principle of life in the heart through new birth (2 Cor. 3:7, Heb. 8:10). The theocracy of external government prefigured an invisible church ruled by Messiah through his Spirit (1 Peter 2:4). The weakness of the old economy, causing hostility between fellow men through the calling out of a literal people, to symbolize the separation of holiness, was superseded by a salvation offered to all nations of who Israel was its servant (Gal 3:8, Heb 8:13).