http://www.scripturecatholic.com/purgatory.html gives 32 Bible verses that tell about purgatory and gives extensive illustration of what the early Church fathers believed.
What part of the whole stain [as you put it] is paid for by Jesus Christ, that you don't understand. You mock His death by suggesting otherwise. I understand you don't realize you mock His death but none the less that is exactly what you are doing. As He said it is finished. There is nothing to be burnt away, it is already washed away by the blood of Christ. My sins are forgiven because I belong to Christ and now I should believe that I have to pay for these forgiven sins. What evil doctrine makes Christ' payment less than it is - full payment.
Not one of those verses refers to purgatory or a process between life here and life in the presence of God for those who belong to Christ. The thief on the cross. Jesus told him you will be with me today in Paradise. Was Jesus going to have to spend some time in this purgatory too. Or was the thief getting special treatment by not having to go to purgatory. NEITHER! The place, process whatever you want to call it does not exist.
How can you not know that Jesus paid the full price of your sins?
I state again the doctrine of purgatory is hated by God, because it is a lie and makes the death of Jesus Christ of no value.
Are you sure that Paradise and heaven are the same thing?
You write of "paying for" the stain of sin. I'm not sure we are taking about the same thing. Jesus has paid in full the debt of our sin. We deserve death. He took the death we deserve. Nevertheless there are certain disabilities consequent upon vice, just as there are abilities which follow the practice of virtue -- no matter how imperfect our motivation for those practices might be.
While miracles happen, the mere act of handing yourself over to Jesus and accepting Him as your Lord and savior does not automatically and inevitably make you an unselfish person, for example. If you tended, say, to the hysterical, to wanting others to notice and discuss amongst themselves and with you what a fabulous, warm, and fuzzy person you are, it's not a sure thing that that habit will die with our conversion or, we maintain, with your death.
Purgatory, as I see it, is where you work off those habits and develop good habits. You are admitted to Purgatory, the front porch of heaven (for yet another metaphor) through the all sufficient merits of Christ. And, as I said, everyone there rejoices because they are saved already because Jesus has already, as you say, paid the full price of their sins.
Saying that something is proved in Scripture or not is always tricky. I find that if all I have is Scripture I do not necessarily come up with Purgatory as a notion. But WITH the doctrine of Purgatory I find many questions answered and passages of Scripture take on what is to me a fuller meaning.
But to be redundantly clear, there is a difference between removing the stain and paying the price. Consequently we can agree with you that forgiveness is supplied through Christ's work alone. We are not saying much about paying a debt except in a sort of double metaphor.
What we are addressing in the doctrine is the fact that people sin a after they are saved. So while something is washed away, there is still something which seems to need a remedy.
What do you think of the sins someone commits after they are saved? My experience is that my relationship with Jesus and my confidence in His saving love drives me to greater awareness of my sinfulness -- and that enables me to begin to pluck out, always with His help (since the root of the problem is usually not asking for His help) the bad habits I have given myself by frequent indulgence in bad deeds.
Now you speak for God?
Aside from ignoring the verses to which you been directed to, you have essentially stated that you have a free pass in life to do whichever your whim points you in whatever amount and for whatever reason and don't have to bear any consequences at all.
That, my friend, is very spiritually dangerous and not a path I'd like my soul wander on down. Jesus did not give you the justification that you can do as you wish "once you are saved." The New Testament is crammed full of verses that tell you what you must do. Attaining eternal life with God is as a result of what you do and don't do. Jesus provided the pathway. But you must walk down it.
Accepting Jesus into you heart and soul is a must. But you must keep Him there. It is possible to reject Him even after accepting Him. I know people who have.