Edot: how is it possible for jesus to have died for the sins of the future, if they hadn't even been commited yet, that part alone is the hardest part to understand, far worse things have happened after jesus died than before.
Because jesus is 100% God and 100% man, he essentially paid for the whole human race, past, present, and future.
This was the entire idea behind the jewish sacrafices, they where a shadow, pointing forward to the inevitable coming of chirst, they did not even know his name, but they knew he was coming, and that they needed his forgivness. Many less learned people assume that the sacrafices where some how for appeasment, when they where instead there to point towards the future redeemer, christ. Killing sheep can not take away you sin, however it could point forward to the lamb of God. We no longer need these shadows because the light has come, and is ready to spread on the earth (and I think we can all agree it has spread) its no coincidence that the temple was destroyed only about 40 years after jesus, death, Jesus,
Matthew 24:1-2
"And Jesus went out, and departed from the temple: and his disciples came to him for to shew him the buildings of the temple.
And Jesus said unto them, See ye not all these things? verily I say unto you, There shall not be left here one stone upon another, that shall not be thrown down."
Matthew 27:50-51 "Jesus, when he had cried again with a loud voice, yielded up the ghost.
And, behold, the veil of the temple was rent in twain from the top to the bottom; and the earth did quake, and the rocks rent;"
Even old testament people from before the time of moses understood this.
Job 19:25
"For I know that my redeemer liveth, and that he shall stand at the latter day upon the earth"
this is from an old testament book, that was written long before jesus came to earth. Probably within a few hundred years after the flood.