Yes, what Jesus did was more than sufficient for
all the purposes that He came to earth to do!
But, when Jesus said, "It is finished!", He meant
that His work/travail on earth was finally finished.
Yes, he had finished/completed/achieved what he came to do - which was to seek and save the lost, Luke 19:10, to give his life as a ransom, Mark 10:45 and to reconcile us to God, Romans 5:11, 2 Corinthians 5:18.
He did not say, or mean, "my work is over so it's over to you now; see if you can achieve salvation with God". Or "I've achieved partial salvation for you; whether you are finally saved, is up to you and your efforts". Or "I've seen to it that my Father will at least think about saving you, but you really need to show him that you want it."
Otherwise, what Good News do we have to share?
"Good News: you are a sinner and cannot save yourself, but if you believe that Christ died in agony for you then there is a way in which you CAN earn your salvation; just believe and work hard for the next 30+ years"?
Or
"Good News: God loves you very much and sent Jesus to die for you - but whether or not you'll ever get to go to heaven, is conditional upon your hard work. God IS like a celestial Santa Claus and you'll only get rewarded if you are very good".
Or
"Good News: you have to EARN salvation from God, just like you've had to try to earn your parent's approval, and almost everything else in your life"?
Some "Good News"!
But the fact is that Christ died for sinners, Romans 5:8. He died for those who were far from God, hated God, could not get near to him and could do nothing to save themselves.
When Adam sinned, mankind's relationship with God was broken. In his mercy, God gave people a way to atone for what they had done so they could be forgiven; the sacrificial system, followed by his law and covenant. But people were unable to keep his law and fully obey him - instead of trying to obey him and not sin, but use the sacrifices for if they DID, people began to take the attitude 'we'll do what we want and repent/offer the correct sacrifice later'.
Yes, deeds are important; they show others, ourselves and God that we mean it when we repented - they are evidence that we have received forgiveness, salvation, eternal life and are living in praise and gratitude to God. Jews in the OT were not doing this. They offered sacrifices, asked for forgiveness and carried on doing the same things as they had before. There are doubtless some today who take the same kind of attitude - "oh, we can always repent later!". THAT is not the mark of someone who has received grace, mercy and the love of God
But that is not the same as saying, "well, you're not saved until the end of your life, and it's only conditional upon the fact that you did enough".
In his mercy, God did what we had no hope of being able to do; reconciled us to himself. The wages of sin is death, Romans 6:23 - we sinned and deserved those wages. Yet he himself offered the sacrifice for our salvation and reconciliation; his son. When Abraham was told to go and offer his son as a sacrifice to God, he was prepared to obey. When Isaac asked where the lamb for the sacrifice was, Abraham replied, "God himself will provide the lamb for the offering", Genesis 22:8.
That was a prophecy and foreshadowing of what was to come. Centuries later, God himself DID provide the Lamb - himself; Jesus the lamb of God who takes away the sin of the world. Reconciliation between man and God complete; eternal life made possible - "it is finished".
I'm Aldebaran.
