Here at The Gospel According to the Gospel it is advocated that the Old Testament saints had our very gospel preached to them. This testimony is not my own. Our New Testament teaches starting with Abraham and Moses the saints of the Old Testament had our gospel, our imputed righteousness, our hope of a savior and our hope of everlasting life.
The Law of Moses that was preached at Mt Sinai was our gospel according to the book of Hebrews. Those saints put their hope in the gospel found in the Law not the Law of the faith. They did not put their hope in the righteousness from the Law but put their hope in the righteousness that God have Abraham and his descendants. Yet these saints still were required to obey the law.
In our day we have those who contend that we need to keep the Ten Commandments. They advocate that we need to not murder, lust, steal, have other gods and we need to keep the Sabbath. Usually with this line of thinking comes a strict observances of the Jewish fest days as well.
Recently I have been told by a believer that people who do not keep the Sabbath are not going to heaven. They use the requirement of the Ten Commandments as our requirement to keep the Sabbath. And of course they think that real believers keep all the feast days as well. They say that not keeping the Jewish Sabbath is breaking the command of God and no Law breaker will get to heaven.
Even though I advocate strongly that the Old Testament has a faith (our gospel) found in the Law, I have never and never will go against scripture and teach that we need to observe any part of the Law to obtain the salvation we hope for.
We have the clear teaching that Christians are not obligated to observe Jewish feast days or the Sabbath. These things have been nailed to the cross along with our sins.
When you were dead in your sins and in the uncircumcision of your sinful nature, God made you alive with Christ. He forgave us all our sins, having canceled the written code, with its regulations, that was against us and that stood opposed to us; he took it away, nailing it to the cross. And having disarmed the powers and authorities, he made a public spectacle of them, triumphing over them by the cross. Therefore do not let anyone judge you by what you eat or drink, or with regard to a religious festival, a New Moon celebration or a Sabbath day. These are a shadow of the things that were to come; the reality, however, is found in Christ.
Those who wish to take these back off of the cross, are you willing to take your sins back off the cross too?
 Colossians 2:13-17