Sometimes a person might think that the Gospel message is directly out of the New Testament and by only studying or believing in the Old Testament and not the New Testament, they are not believing in, agreeing with, or looking forward to the gospel message. Let's look at the gospel message and see where it gets its Jewish roots.
A great starting point for the gospel message is acknowledging what a persons current status is. I have heard someone say that they don't need to be "saved" from anything. This may come from a variety of thoughts but included in these thought is that somehow God has or will forgive them because of something they have done. Could be good deeds (works), could be prayers, (like during Jewish high holidays where a person is expected to be written in the Book of life), or other reasons as well.
...for all have sinned and fall short of the glory of God, (Romans 3:23)
But we are all as an unclean thing, and all our righteousnesses are as filthy rags; (Isaiah 64:6)
For the wages of sin is death, (Romans 6:23)
When man had only 1 rule to live by, the breaking of that rule meant death.
...for in the day that you eat of it (from the tree of knowledge in the Garden of Eden) you shall surely die. (Genesis 2:17)
...But your iniquities have separated you from your God; your sins have hidden his face from you, so that he will not hear. (Isaiah 59:2)
...the soul who sins is the one who will die. (Ezekiel 18:4)
“He himself bore our sins” in his body on the cross, so that we might die to sins and live for righteousness; “by his wounds you have been healed.” (1 Peter 2:24)
Concerning Temple sacrifices (designed for the animal to take our place) the Old Testament teaches:
For the life of a creature is in the blood, and I have given it to you to make atonement for yourselves on the altar; it is the blood that makes atonement for one’s life. (Leviticus 17:11)
The Prophet Isaiah foretold the death of our Messiah as our substitutional sacrifice.
Surely he took up our pain and bore our suffering, yet we considered him punished by God, stricken by him, and afflicted. But he was pierced for our transgressions, he was crushed for our iniquities; the punishment that brought us peace was on him, and by his wounds we are healed. (Isaiah 53:4-5)
Read More About Isaiah 53
But now Jesus has obtained a superior ministry, since the covenant that he mediates is also better and is enacted on better promises. (Hebrews 8:6)
“The days are coming,” declares the Lord, “when I will make a new covenant with the people of Israel and with the people of Judah. It will not be like the covenant I made with their ancestors when I took them by the hand to lead them out of Egypt, because they broke my covenant, though I was a husband to them,” declares the Lord....“For I will forgive their wickedness and will remember their sins no more.” (Jeremiah 31:31-34)
Take A Closer Look At The New Covenant.
For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life. (John 3:16)
Multitudes who sleep in the dust of the earth will awake: some to everlasting life, others to shame and everlasting contempt. (Daniel 12:2 - In the Hebrew text it is Daniel 12:1)
The Book of Life is mentioned first in the Old Testament (Exodus 32:32),
and then reconfirmed again in the New Testament (Revelations. 20:11-15).
Other articles of interest include: