Adam Clarke's Commentary on the Bible

Verse 7 (Exodus 20:7)

Thou shalt not take the name of the Lord thy God in vain - This precept not only forbids all false oaths, but all common swearing where the name of God is used, or where he is appealed to as a witness of the truth. It also necessarily forbids all light and irreverent mention of God, or any of his attributes; and this the original word לשוא lashshav particularly imports: and we may safely add to all these, that every prayer, ejaculation, etc., that is not accompanied with deep reverence and the genuine spirit of piety, is here condemned also. In how many thousands of instances is this commandment broken in the prayers, whether read or extempore, of inconsiderate, bold, and presumptuous worshippers! And how few are there who do not break it, both in their public and private devotions! How low is piety when we are obliged in order to escape damnation, to pray to God to "pardon the sins of our holy things!" Even heathens thought that the names of their gods should be treated with reverence. Παντως μεν δη καλον επι ηδευμα, θεων ονοματα μη χραινειν ῥᾳδιως, εχοντα ὡς εχουσιν ἡμων ἑκαστοτε τα πολλα οἱ πλειστοι καθαροτητος τε και ἁγνειας τα περι τους θεους . "It is most undoubtedly right not easily to pollute the names of the gods, using them as we do common names; but to watch with purity and holiness all things belonging to the gods."

The Lord will not hold him guiltless, etc. - Whatever the person himself may think or hope, however he may plead in his own behalf, and say he intends no evil, etc.; if he in any of the above ways, or in any other way, takes the name of God in vain, God will not hold him guiltless - he will account him guilty and punish him for it. Is it necessary to say to any truly spiritual mind, that all such interjections as O God! my God! good God! good Heavens! etc., etc., are formal positive breaches of this law? How many who pass for Christians are highly criminal here!

- Adam Clarke's Commentary on the Bible