Matthew Poole and continuators on James 5:12

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 .

Because it is a great Sin to swear upon every slight occasion, and it was very usual among the Jews, and it was the more difficult to bring them off from it who were so much accustomed to it; therefore the Apostle commands them, that above all things they should not Swear, i. e. should take special care they did not, and watch diligently against a Sin so many were addicted to, and into which they might so easily fall.

All Swearing is not forbidden any more than Matth. 5.34. (for Oaths are made use of by Holy Men both in the Old and New Testament, Gen. 21.23, 24. and 24.3. and 26.28. and 1 King. 17, 1, 2. and 2 Cor. 1.23. and Gal. 1.20. and the use of an Oath is permitted, and approved of by God himself, Psal. 15.4. Heb. 6.16.) but such Oaths as are false, rash, vain, without just cause, or customary and frequent in ordinary Discourse, 1 King. 19.2. Ier. 5.2. Matth. 5.37.

By which the Jews thought they might lawfully Swear, as likewise by other Creatures so the Name of God were not interposed; not considering that where it is not expressed yet it is implied, Matth. 23.20, 21.

Viz. Of the like kind.

Either, 1. Let your Speech be Yea, Yea, and Nay, Nay, i. e. by plain affirmations and negations, without the addition of any Oath, for confirmation, Matth. 5.37. Or, 2. Let your Yea be yea, and your Nay nay, i. e. Let your Words be in Truth and Sincerity, your Speech seconded by your Actions; accustom your selves to truth and plainness in speaking, and that will take away the occasion of Swearing. See the like, 2 Cor. 1.17, 18, 19.

Viz. for taking the Name of God in vain, Exod. 20.7. which is always done in an unwarrantable Oath.

Marginal references: Mat. 5.34.