Matthew 5:34
But I say unto you, Swear not at all; neither by heaven; for it is God's throne:
But I say unto you, swear not at all,.... Which must not be understood in the strictest sense, as though it was not lawful to take an oath upon any occasion, in an affair of moment, in a solemn serious manner, and in the name of God; which may be safely done: but of rash swearing, about trivial matters, and by the creatures; as appears by what follows,
neither by heaven; which is directly contrary to the Jewish canons {m}, which say,
"they that swear Mymvb, "by heaven", and by earth, are free.''
Upon the words in Song of Solomon 2:7, "I adjure you", &c. it is asked {n},
"by what does she adjure them? R. Eliezer says, by the heavens, and by the earth; by the hosts, the host above, and the host below.''
So Philo the Jew says {o} that the most high and ancient cause need not to be immediately mentioned in swearing; but the "earth", the sun, the stars, ouranon, "heaven", and the whole world. So R. Aben Ezra, and R. David Kimchi, explain Amos 4:2. "The Lord God hath sworn by his holiness"; that is, say they, Mymvb, "by heaven": which may be thought to justify them, in this form of swearing; though they did not look upon it as a binding oath, and therefore if broken they were not criminal {p}.
"He that swears Mymvb by heaven, and by the earth, and by the sun, and the like; though his intention is nothing less than to him that created them, this is no oath.''
The reason why it is forbidden by Christ to swear by heaven, is,
for it is God's throne; referring to Isaiah 66:1 where he sits, the glory of his majesty shines forth, and is itself glorious and excellent, and not to be mentioned in a vain way; and especially, for the reason Christ elsewhere gives, Matthew 23:22 that "he that shall swear by heaven, sweareth by the throne of God, and by him that sitteth thereon"; so that they doubly sinned, first, by openly swearing by that which is God's creature; and then, by tacitly bringing God into their rash and vain oaths.
{m} Misn. Shebuot, c. 4. sect. 13.
{n} Shirhashirim Rabba, fol. 10. 4.
{o} De Special. leg. p 770.
{p} Maimon. Hilch. Shebuot, c. 12. sect. 3.