The speaker is John the Baptist; and he is commenting on his cousin - Jesus Christ. It was something that God, by inspiration of His Spirit, must have given him an understanding of. We know that this took place after John baptized Jesus.
That ought to give you, at least, a beginning of an insight (maybe a great deal of insight) and discernment regarding the importance of the death of Jesus Christ. One death of one man - the sacrifice of a life that was sinless - is capable, in the eyes of God, of equalizing and making of no account all of the sins of all of mankind for all of the time that man has been sinning!
It is interesting to see the way sin is looked at in the New Testament. And that is, that sin is seen as an infectious disease - something that has gotten into a person and something that that person is capable of 'passing on' to someone else. In other words, they can 're-infect' another person; and that person will then be a carrier of this disease too. It is something that is internal, but it is something that can be spread.
We might think of it in terms of AIDS (because that is on all of our minds). We fear AIDS, do we not? We want to be separated from AIDS, do we not? So, you see that lurking in the background of this view of sin is the idea of quarantine. As long as a person was infected with a disease, they were quarantined away from other people; and they had no relationship with those who were clean (in the Old Testament sense). That is because those who were clean did not want to become infected by those who were defiled by the disease.
Jesus, then, is seen as the cure that will enable this infected person to come out of their quarantine and, thus, have a relationship with others. In this case, they are introduced to a relationship with God! It is a beautiful, very interesting, and colorful picture.
If we can understand it, that is the kind of effect that this sacrifice will have upon all of the sins of all of mankind - every individual who has ever lived! Jesus Christ's sacrifice is the cure that will enable these people, who have been quarantined away, to move into a relationship with God.
Tie these two verses together. You have a very clear description of the place that Jesus Christ played in the type that was enacted out (all the way back in Exodus 12) some fourteen, or fifteen, hundred years prior to its actual occurrence. Jesus Christ is the true Passover Lamb sacrificed for the entire world, in order that God may pass over the sins of all of mankind.
How long was this on God's mind? That is, His purpose of having a sacrifice - thus enabling Him to pay for the sins of mankind? We know that sin kills. And, if a person is required to pay for his own sin, then he dies - because the wages of sin is death. [Romans 6:23] Well, God purposed (it says, long before the foundation of the world) that once sin began, the only way that it could be paid for would be through the death of either (1) the individual who sinned, or (2) a substitution who could take the place of those who sinned. But that substitution had to be sinless! And we find that this death had to be of One who was greater than all of the creation.
There is the payment. And from the foundation of the world God had this in mind. Without the sacrifice of Jesus Christ as our (or, mankind's) Passover, there is no remission of sins - no forgiveness of sins, by God the Father. And so we find that this event is the beginning of eternal life for us. Without it, there is no eternal life - because each person then will die in his sins, because he will then be required to pay for his own sins, himself.
