But Jesus, knowing their thoughts, said, "Why do you think evil in your hearts? For which is easier, to say, 'Your sins are forgiven,' or to say, 'Rise and walk'? But that you may know that the Son of Man has authority on earth to forgive sins"-he then said to the paralytic-"Rise, pick up your bed and go home."
How were people saved before Jesus died? The same way we are not saved, by His blood. The cross is such a fixed certainty, that it could be trusted in advance to compete its work just as it can now be trusted in retrospect for what it did.
During Jesus' earthly ministry He forgave sins. On what basis? His blood. But how so? His blood wasn't poured out yet. It was still pumping through His veins and animating His person with vitality. Yet, the certainty of the Savior's submission and the perfection of the Father's plan was so secure, it could forgive sins even while the Sacrifice walked and talked. Sins were forgive on the basis of what He would do. His blood was always as good as poured. So certain, in fact, that Jesus could forgive sins in the present for what He was going to do in the future.
The cross was never a question. It was always a fixed linchpin on which past, present, and future sin is forgiven completely.
Our sins are forgiven on the certainty of the cross.