harp upon

Some sense of the grimly-ludicrous moved me to a fretful laugh, as I replied, “I have looked over it. In Heaven’s name, don’t harp upon it!”

But Joe had got the idea of a present in his head and must harp upon it.

For some reason this talk about his health was not welcome to him, angered him even, and I thought it tactless of Beatrice to harp upon it in this way, making so big a point of it.

"You can't really predict when somebody is gonna be in a really bad situation, that's why we really harp upon knowing the conditions of where you're about to go," spokesman Brady Smith said.

Ben, you harp upon this money of Marmaduke's; but let me tell you that I don't know what I should have done without it.