Matthew Poole and continuators on Jeremiah 5:2

2 And though they say, the LORD liveth, surely they swear falsely.

Though when they swear, they use the form of an Oath, and say the Lord liveth, chap. 4.2. or by the living God, by swearing here we may understand all their service of God by a Synecdoche, swearing being a part of Gods Worship.

Yet, or therefore they swear falsly, either they swear to that which is false, or, if to that which is true, they are so perfidious to me, that they do it deceitfully, not in sincerity, and in reverence to that Holy Name by which they swear, possibly they may often speak of God, and not swear by false gods, verse 7. but it is all but hypocrisie and deceit, Isa. 48.1 chap. 12.2. and 42.5, 20. 2 Tim. 3.5. It is neither in truth nor righteousness, two of the principal qualifications of a lawful Oath, thus prostituting the name of God, making themselves guilty, not of hypocrisie only, but Sacriledge.