What does the tenth commandment require of us?

Heidelberg Catechism (extended)

The Catechism
Method of Instruction in the Christian Religion
As the Same is Taught in the Reformed Churches and Schools

(with the Scripture references written out)

Note. This Catechism is fully based on the Scriptures. The references to Scripture are indicated in parentheses with a letter. For example, the letter (a) points to the texts (a) placed after the answer.

44. Lord's Day 

Q. 113. What does the tenth commandment require of us? 

A. That even the smallest inclination or thought, contrary to any of God's commandments, never rise in our hearts; but that at all times we hate all sin with our whole heart, and delight in all righteousness. (a) 

(a) Rom.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. 

Q. 114. But can those who are converted to God perfectly keep these commandments? 

A. No: but even the holiest men, while in this life, have only a small beginning of this obedience; (a) yet so, that with a sincere resolution they begin to live, not only according to some, but all the commandments of God. (b) 

(a) 1 John 1:8 If we say that we have no sin, we deceive ourselves, and the truth is not in us. 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. 1 John 1:10 If we say that we have not sinned, we make him a liar, and his word is not in us. Rom.7:14 For we know that the law is spiritual: but I am carnal, sold under sin. Rom.7:15 For that which I do I allow not: for what I would, that do I not; but what I hate, that do I. Eccl.7:20 For there is not a just man upon earth, that doeth good, and sinneth not. 1 Cor.13:9 For we know in part, and we prophesy in part. 

(b) Rom.7:22 For I delight in the law of God after the inward man: Ps.1:2 But his delight is in the law of the LORD; and in his law doth he meditate day and night. James 2:10 For whosoever shall keep the whole law, and yet offend in one point, he is guilty of all. 

Q. 115. Why will God then have the ten commandments so strictly preached, since no man in this life can keep them? 

A. First, that all our lifetime we may learn more and more to know (a) our sinful nature, and thus become the more earnest in seeking the remission of sin, and righteousness in Christ; (b) likewise, that we constantly endeavour and pray to God for the grace of the Holy Spirit, that we may become more and more conformable to the image of God, till we arrive at the perfection proposed to us, in a life to come. (c) 

(a) Rom.3:20 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. 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. Ps.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. 

(b) Matt.5:6 Blessed are they which do hunger and thirst after righteousness: for they shall be filled. Rom.7:24 O wretched man that I am! who shall deliver me from the body of this death? Rom.7:25 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. 

(c) 1 Cor.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. Philip.3:11 If by any means I might attain unto the resurrection of the dead. Philip.3:12 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. Philip.3:13 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, Philip.3:14 I press toward the mark for the prize of the high calling of God in Christ Jesus.

Source: http://www.ccel.org/creeds/heidelberg-cat-ext.txt