What is required in the third commandment?

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.

36. Lord's Day

Q. 99. What is required in the third commandment? 

A. That we, not only by cursing (a) or perjury, (b) but also by rash swearing, (c) must not profane or abuse the name of God; nor by silence or connivance be partakers of these horrible sins in others; (d) and, briefly, that we use the holy name of God no otherwise than with fear and reverence; (e) so that he may be rightly confessed (f) and worshipped by us, (g) and be glorified in all our words and works. (h) 

 (a) Lev.24:11 And the Israelitish woman's son blasphemed the name of the LORD, and cursed. And they brought him unto Moses: (and his mother's name was Shelomith, the daughter of Dibri, of the tribe of Dan:) Lev.24:12 And they put him in ward, that the mind of the LORD might be shewed them. Lev.24:13 And the LORD spake unto Moses, saying, Lev.24:14 Bring forth him that hath cursed without the camp; and let all that heard him lay their hands upon his head, and let all the congregation stone him. Lev.24:15 And thou shalt speak unto the children of Israel, saying, Whosoever curseth his God shall bear his sin. Lev.24:16 And he that blasphemeth the name of the LORD, he shall surely be put to death, and all the congregation shall certainly stone him: as well the stranger, as he that is born in the land, when he blasphemeth the name of the LORD, shall be put to death. 

(b) Lev.19:12 And ye shall not swear by my name falsely, neither shalt thou profane the name of thy God: I am the LORD. 

(c) Matt.5:37 But let your communication be, Yea, yea; Nay, nay: for whatsoever is more than these cometh of evil. James 5:12 But above all things, my brethren, swear not, neither by heaven, neither by the earth, neither by any other oath: but let your yea be yea; and your nay, nay; lest ye fall into condemnation. 

(d) Lev.5:1 And if a soul sin, and hear the voice of swearing, and is a witness, whether he hath seen or known of it; if he do not utter it, then he shall bear his iniquity. Prov.29:24 Whoso is partner with a thief hateth his own soul: he heareth cursing, and bewrayeth it not. 

(e) Jer.4:2 And thou shalt swear, The LORD liveth, in truth, in judgment, and in righteousness; and the nations shall bless themselves in him, and in him shall they glory. Isa.45:23 I have sworn by myself, the word is gone out of my mouth in righteousness, and shall not return, That unto me every knee shall bow, every tongue shall swear. 

(f) Rom.10:9 That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved. Rom.10:10 For with the heart man believeth unto righteousness; and with the mouth confession is made unto salvation. Matt.10:32 Whosoever therefore shall confess me before men, him will I confess also before my Father which is in heaven. 

(g) Ps.50:15 And call upon me in the day of trouble: I will deliver thee, and thou shalt glorify me. 1 Tim.2:8 I will therefore that men pray every where, lifting up holy hands, without wrath and doubting. 

(h) Rom.2:24 For the name of God is blasphemed among the Gentiles through you, as it is written. 1 Tim.6:1 Let as many servants as are under the yoke count their own masters worthy of all honour, that the name of God and his doctrine be not blasphemed. Col.3:16 Let the word of Christ dwell in you richly in all wisdom; teaching and admonishing one another in psalms and hymns and spiritual songs, singing with grace in your hearts to the Lord. Col.3:17 And whatsoever ye do in word or deed, do all in the name of the Lord Jesus, giving thanks to God and the Father by him. 

 Q. 100. Is then the profaning of God's name, by swearing and cursing, so heinous a sin, that his wrath is kindled against those who do not endeavour, as much as in them lies, to prevent and forbid such cursing and swearing? 

A. It undoubtedly is, (a) for there is no sin greater or more provoking to God, than the profaning of his name; and therefore he has commanded this sin to be punished with death. (b) 

 (a) Prov.29:24 Whoso is partner with a thief hateth his own soul: he heareth cursing, and bewrayeth it not. Lev.5:1 And if a soul sin, and hear the voice of swearing, and is a witness, whether he hath seen or known of it; if he do not utter it, then he shall bear his iniquity. 

(b) Lev.24:15 And thou shalt speak unto the children of Israel, saying, Whosoever curseth his God shall bear his sin. Lev.24:16 And he that blasphemeth the name of the LORD, he shall surely be put to death, and all the congregation shall certainly stone him: as well the stranger, as he that is born in the land, when he blasphemeth the name of the LORD, shall be put to death.

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