Heidelberg Catechism · 1563

Q115. If in this life no one can keep the ten commandments perfectly, why does God have them preached so strictly?

First, that throughout our life we may more and more become aware of our sinful nature, and therefore seek more eagerly the forgiveness of sins and righteousness in Christ. Second, that we may be zealous for good deeds and constantly pray to God for the grace of the Holy Spirit, that He may more and more renew us after God's image, until after this life we reach the goal of perfection.
Answer · Heidelberg Catechism

Scripture proofs

  1. [1]
    Psalms 32:5

    I acknowledged my sin unto thee, and mine iniquity have I not hid. I said, I will confess my transgressions unto the Lord; and thou forgavest the iniquity of my sin. Selah.

    Romans 3:19-26

    Now we know that what things soever the law saith, it saith to them who are under the law: that every mouth may be stopped, and all the world may become guilty before God. Therefore by the deeds of the law there shall no flesh be justified in his sight: for by the law is the knowledge of sin. But now the righteousness of God without the law is manifested, being witnessed by the law and the prophets; …

    Romans 7:7

    What shall we say then? Is the law sin? God forbid. Nay, I had not known sin, but by the law: for I had not known lust, except the law had said, Thou shalt not covet.

    Romans 7:24-25

    O wretched man that I am! who shall deliver me from the body of this death? I thank God through Jesus Christ our Lord. So then with the mind I myself serve the law of God; but with the flesh the law of sin.

    1 John 1:9

    If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.

  2. [2]
    1 Corinthians 9:24

    Know ye not that they which run in a race run all, but one receiveth the prize? So run, that ye may obtain.

    Philippians 3:12-14

    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.

    1 John 3:1-3

    Behold, what manner of love the Father hath bestowed upon us, that we should be called the sons of God: therefore the world knoweth us not, because it knew him not. Beloved, now are we the sons of God, and it doth not yet appear what we shall be: but we know that, when he shall appear, we shall be like him; for we shall see him as he is. And every man that hath this hope in him purifieth himself, even as he is pure.

Proof texts as given in the original; verse text from the King James Version.