Sorry it took awhile to get back here.
God is infinite.
So if we sin against God . . . .
Do we just sin against “part” of God? Or . . . .
Do we sin against God (ALL of God)?
We sin against ALL of God.
God is perfectly merciful but He is also perfectly JUST. God’s very nature requires an account to be paid for sins against Him.
HOW in the world can we FINITE beings pay for ANY of our sins? After all, we’d have to pay an infinite account.
We cannot offer God a perfect infinite sacrifice.
So what is going to happen?
Be careful at this point.
Protestants will often say: “Jesus suffered and offered an infinite sacrifice . . . . so I don’t have to offer anything. Jesus does it all”
This is a partial truth.
We cannot offer an infinite sacrifice. That is true (we are finite beings).
Incidentally. This is one (among many) reasons why the Jehovah’s Witnesses MUST be wrong about Jesus being mere St. Michael the Archangel. St. Michael is a finite being. St. Michael is a mere angel. We too are finite beings. Jesus is NOT St. Michael the archangel (despite the Witnesses claim that He is). Jesus is not a mere finite being. Jesus has a Divine nature and a human nature.
If St. Michael could offer a perfect sacrifice to God, that would infer that “Jehovah God” is finite. That doctrine of the Jehovah’s Witnesses makes God out to be a puny finite being in essence (although the Witnesses wouldn’t put it that way).
Jesus offers Himself as an infinite sacrifice to the Father on our account. This is true (this is one way we know Jesus is true God and true Man and the Fathers used this argument in the early Church against the Arian heretics according to Scott Hahn).
But does this mean we don’t have to offer ANYTHING?
We must offer ourselves UNITED to Christ. We need to be IN-Jesus.
So Jesus takes our offering and unites it to Himself–literally (ordinarily through the Sacraments) and our sacrifice becomes united to Jesus and HIS atoning sacrifice.
Again. Many apologies to take this long in getting back here. My first response was a one finger deal on the android device (this is at the computer and afford me an opportunity to put down more).
I hope this helps.