I can think of no better Bible passage which teaches the concept of two types of forgiveness than one which includes the words of the Lord Jesus himself, who is the provider of forgiveness to all by virtue of his redemptive blood which was shed at Calvary.
From the NASB Updated Bible:
Jesus, knowing that the Father had given all things into his hands, and that He had come forth from God and was going back to God, got up from supper, and laid aside His garments; and taking a towel, He girded Himself. Then He poured water into the basin, and began to wash the disciples' feet and to wipe them with the towel with which He was girded. So He came to Simon Peter, He said to him, "What I do you do not realize now, but you will understand hereafter." Peter *said to Him, "Never shall You wash my feet!" Jesus answered him, "If I do not wash you, you have no part with Me." Simon Peter said to Him, "Lord, then wash not only my feet, but also my hands and my head." Jesus *said to him, "He who has bathed needs only to wash his feet, but is completely clean; and you are clean but not all of you [i.e., Judas Iscariot] (John 13:3-10, with italics and asterisks provided by the NASB).
We're all familiar, I suppose, with some of the cultural factors at work in this passage. In Jesus' day, the servant in a household having many servants is charged with washing the feet of visitors to the master's house. He has the lowest, most menial job a servant can have (go here for some basic information, and follow the links provided there).
[Interestingly (but incidentally) another footwashing incident took place in the home of Simon the Pharisee, as recorded in Luke 7:36-50, and of the three observations Jesus made (in vv.44-46), the first one was this:
I entered your house; you gave Me no water for my feet (v.44),
which makes the reader wonder why Jesus did not say, "You asked no servant to wash my feet." Perhaps Simon simply forgot to have this service performed for Jesus, or perhaps Simon had no servants, or the servant in charge of footwashing was ill or out of the house. Whatever the case might be, footwashing was common and expected in Jesus' day.]
Now to the heart of the first passage. We could easily say, "Oh that impetuous Peter. He's always putting his mouth in gear before his brain." That would be true, for the most part. Peter did have a way of making promises he could not (or would not) keep (see Mark 14:29-31; note, too, that all the disciples were saying the same thing Peter said, so Peter was evidently not alone in his exclamation).
Nevertheless, Peter's exclamation in John 13 became the basis for Jesus distinguishing between two types of cleansing, both of which I (and many others) take to be synonymous with forgiveness, for to be "cleansed from all unrighteousness" is to be forgiven by God (see 1 John 1:9). Moreover, the existential reality of God's forgiveness for any repentant sinner is to know that God will never again bring up the confessed- and repented-of sin to rub in our faces. When God forgives, He forgets (an anthropomorphism which means simply that God's forgiveness has no strings attached--but more on that later. See Isaiah 43:25).
Our Standing Versus Our State
The first cleansing is the cleansing of the entire body, which Jesus referred to as being "bathed" (13:10). This cleansing is symbolic of the cleansing of conversion, or the new birth. Once we are born again, our standing in Christ is assured. Paul calls this cleansing
"the washing of regeneration" (Titus 3:5).
No one can see the kingdom of God, Jesus warned Nicodemus (John 3:3), without that regeneration, or new birth. Put differently, Jesus said,
Truly, truly I say to you [, Nicodemus], unless one is born of water and the Spirit he cannot enter into the kingdom of God (John 3:5).
Both in John 3 and John 13 Jesus was quite clear, I believe, that a "positional" forgiveness, such that a person is fit for heaven, is a once-in-a-lifetime experience (particularly according the OSAS believers!). God's number one criterion regarding a person's fitness for heaven, so to speak, is for that person to be declared innocent by God. This declaration is often referred to in Scripture as justification, or being justified (Romans 2, 3, 4, 5, and 8, for example).
In other words, when the Judge of all the earth declares someone righteous, that person becomes fit for heaven indeed. The analogy of the judge and the guilty criminal breaks down, of course, at least in a secular setting, since an earthly judge's pronouncement of innocence can be overturned. That, however, is the nature of virtually every analogy.
The second kind of cleansing is the partial cleansing of just the feet. This cleansing speaks of relational forgiveness, since throughout our various journeys in life, our feet do get dirty!
At the risk of being impolitic, I offer this analogy. Suppose you just emerged from your daily bath or shower. You dry yourself off, wrap a towel around your waist, and step onto the porch of your house, just to soak in the sun briefly, prior to getting fully dressed.
Unbeknownst to you, your pet dog just had an "accident" on your porch, and the moment your foot touches the porch, you feel something warm and squishy between your toes. (Need I say more?!). What will you do next (apart from uttering a few choice epithets!)? Will you jump into the bathtub again and take another bath? Not likely. You would, however, take care to wash the offending foot very thoroughly.
The application of this analogy is clear. A person who is justified in the eyes of God and who sins again after being declared righteous will never hear his Judge say, "I take back your justification. No soup [--I mean--] no salvation for you!"
God the Judge will clearly be disappointed. Moreover, we can certainly grieve, lie to, and put the Holy Spirit to the test by sinning (see Acts 5:3 and 9; Ephesians 4:30). Fellowship (not justification) with God (not justification by God) can be restored through frequent confession, since no child of God, as the apostle John points out, can say in truth, "I am without sin" (1 John 1:5-10, especially v.8).
Peter and all who embrace Jesus Christ as Savior and Lord, have taken a bath in the cleansing blood of Christ and are clean every whit. That is positional forgiveness, or the forgiveness which gives us our standing in Christ. All believers in Jesus Christ who sin after conversion (and we all do--and will) need to confess to God (which is simply to agree with God) that they have sinned, preferably as soon as it happens. Again, that sin does not affect their standing in Christ, but it certainly affects our spiritual state at the time it occurs. The effect is broken fellowship with Christ.
The good news, however, is that With confession comes the cleansing from all unrighteousness of which John speaks in his first letter (1:9).
That experiential, existential, relational forgiveness harkens back, of course, to the positional and judicial forgiveness which Jesus proffers to all who call upon the name of the Lord to be saved. That is why John says that God
". . . is faithful and just to forgive our sins and to cleanse us . . .."
The faithful and just character of God demands relational forgiveness because that forgiveness was accomplished once and for all at Calvary. For God to refuse to forgive any confessed sin is clearly impossible. He will always, for all eternity, look back (so to speak) to what his Son accomplished on the cross, and then forgive us and cleanse us, for Jesus' sake. Again, he is faithful, and he keeps his promises forever.
In conclusion, my godly grandfather was more than happy to share his conversion story with anyone, any time. As a child growing up in England, he was reared by Christian parents and was taken to church regularly. At a certain age, however, which was probably when he was quite young and still living at home, he claimed Psalm 51:7 for his own. It reads,
Purify me with hyssop, and I shall be clean; Wash me, and I shall be whiter than snow (NASB Updated).
Or in the KJV, which my grandfather read exclusively,
Purge me with hyssop, and I shall be clean: wash me, and I shall be whiter than snow.
God hears the prayer of the penitent, and he justifies the one who asks to be forgiven, even if the only words uttered (or thoughts, thought) are,
God, be merciful to me, a sinner (Luke 18:13).