1 Kings 20:35-43

I think the idea is...We've got to do what Yahweh instructs us to, no matter how hard it is.

The prophet, being instructed by Yahweh, told the other prophet to strike him, and when he didn't, was immediately punished.
The prophet then presented a scenario to Ahab, which allowed Ahab to judge, and with his own judgement he was punished, (similar to Nathan and David)

2Sa 12:1 And the LORD sent Nathan unto David. And he came unto him, and said unto him, There were two men in one city; the one rich, and the other poor.
2Sa 12:2 The rich man had exceeding many flocks and herds:
2Sa 12:3 But the poor man had nothing, save one little ewe lamb, which he had bought and nourished up: and it grew up together with him, and with his children; it did eat of his own meat, and drank of his own cup, and lay in his bosom, and was unto him as a daughter.
2Sa 12:4 And there came a traveller unto the rich man, and he spared to take of his own flock and of his own herd, to dress for the wayfaring man that was come unto him; but took the poor man's lamb, and dressed it for the man that was come to him.
2Sa 12:5 And David's anger was greatly kindled against the man; and he said to Nathan, As the LORD liveth, the man that hath done this thing shall surely die:
2Sa 12:6 And he shall restore the lamb fourfold, because he did this thing, and because he had no pity.
2Sa 12:7 And Nathan said to David, Thou art the man......
2Sa 12:10 Now therefore the sword shall never depart from thine house; because thou hast despised me, and hast taken the wife of Uriah the Hittite to be thy wife.