The Lord's Prayer in the Judgment Hour
God could indeed instantly give the repentant believing Christian sinless perfection and make him sinless in sanctification. He could indeed instantly completely remove the old sinful nature so that we would never have to wrestle and fight and struggle against sin and have to repent daily and ask for forgiveness daily for the remainder of our lives.
However, the fact is that the word of God clearly teaches us that all believers must repent daily of their shortcomings and bow daily at the foot of the cross in repentance. These are lessons of repentance and trusting in the imputed righteousness of Christ which are not learned experientially in a moment. This lesson must be learned over and over and over for a life-time so that it finally sinks into our deceitful and desperately wicked hearts that there is only One who is righteous and who can stand before the full glory of the righteousness of God and that One is our Lord Jesus Christ who is the fullness of the glory of God and who alone is worthy of the kingdom and the power and the glory and the majesty now and forever more. Because of the slowness of our hearts and the hardness of our hearts, God has seen fit in His wisdom to require us to daily re-learn the lesson of the Gospel so that God's people throughout eternity will never again repeat the Mystery of Iniquity begun by Satan.
Lucifer's pride and arrogance lead him to believe that he, in himself, was righteous enough to stand before the full glory of the righteousness of God and not need to acknowledge his dependence upon the Lord Jesus Christ, the eternal Word of God, as the One mediator between the creature and the Creator.
God has given nearly 6,000 years for the human family to learn the lesson of justification by faith before the holiness of God and that we will always need to approach God only through the Lord Jesus Christ. It is for this reason that we offer all our prayers "through Jesus Christ our Lord". In the sight of God there is none righteous, no not one. As even righteous Job had to confess when God revealed all His glory to him, "Behold I am vile!" Even the unfallen angels of heaven must veil their eyes before the glory of God and His eternal righteousness. Thus the truth of justification by faith in Christ shall be a lesson which remains throughout eternity for all of the created beings in all the universe. In the presence of His eternal righteousness, all must acknowledge, "Only God is good".
These are not lessons that one learns in one day, but rather the truth must be learned through many bitter lessons of agonizing conflict and struggle with our sinful stubborn will and nature. The lesson of Romans 7 is the lesson of a life-time and it is for this reason that God in His infinite wisdom does not completely remove the old sinful nature from the believer. It is for this reason that the Lord said when Man was expelled from Eden, "Cursed be the ground for THY SAKE." The hard old soil, as an allegory of the fallen human heart, would now require sweat and toil to pull up the weeds and the tares and this would require a lifetime of discipline and patience and diligence and perseverance through repentance towards God and faith in His redeeming imputed grace. Character is developed in the school of affliction and the furnace of the fires of hardship. We are to be students in this school for a life-time. Only the wisdom of our eternal Father could have devised so complete a salvation for the fallen sons and daughters of Adam.
In this life there is hardship and tears, but by taking up our cross and following our great exalted Head we will be lead out of this valley of the shadow of death and one day stand on the sea of glass before His throne. There we will cast our crowns down before Him and declare that we are unworthy to be there. This is the song of Moses which no man can sing but those who have come out of great tribulation and washed their robes white in the blood of the Lamb.
Thus justification is the work of a moment, while sanctification is the work of a life-time. Regarding the attainment of sinless perfection, we are always to say with Paul, "Not as though I had already attained, either were already perfect: but I follow after, if that I may apprehend that for which also I am apprehended of Christ Jesus. Brethren, I count not myself to have apprehended: but this one thing I do, forgetting those things which are behind, and reaching forth unto those things which are before, I press toward the mark for the prize of the high calling of God in Christ Jesus." Philippians 3:11ff