Good point! And very true...Abraham was justified by faith. David was a "man after God's own Heart". All through the OT, there are examples of people saved by faith, just as we are. I do not hold with the idea that OT saints were not able to be saved the same way we are. The issue is not the words we say (the sinner's prayer, etc.) but the attitude of the heart. Our salvation is based on the imputation of the righteousness of God to those who, in repentance, turn to God and acknowledge their complete inability to save themselves, and rely on and look to God to rescue them from their sinful state. Jesus made a way for us to receive the ongoing forgiveness of sins and ongoing imputation of the righteousness of God through His sacrifice of Himself at Calvary. It can be boiled down to this: salvation is a matter of position. We are either "in Adam", i.e. sinful, sinners by nature (whether or not we have actually committed a sin), or we are "in Christ", i.e. justified, clothed with the righteousness of Christ, which is God's own righteousness. God sees us in that fashion. If we are "in Christ" we have access to the Father, to the benefits of His Mercy, Grace, and Blessing, or we are "in Adam", subject to the imputation of sin, the curse of sin, and the certain judgement against all who sin and rebel against God, both Man and Angel. There really is no middle ground. We are either "in Christ" or "in Adam".
To be sure, we must not assume that it is a "once done, never changed" transaction that allows us then to continue living the way we did before. Paul dealt with that notion in several of his letters to the churches. There is the aspect of "abiding" in Christ's teachings and Word, which would be the natural result of true conversion. If you have truly repented, you could not continue to go the same way as before. If one turns (repents) as one is walking, by necessity one is going in a different direction than before. It cannot be otherwise.
oppps be prepared to get hit on this one..*grin*..that is a bit more Wesleyan thought than most here care to hear