Charles Ellicott Commentary Jeremiah 23:38

"But if ye say, The burden of Jehovah; therefore thus saith Jehovah: Because ye say this word, The burden of Jehovah, and I have sent unto you, saying, Ye shall not say, The burden of Jehovah;" — Jeremiah 23:38 (ASV)

But since you say. —Better, if you say.