Thanks for your input and examples. Is there any indication in the Samuel passage that the Egyptian slave really hadn’t eaten for three days and three nights? It seems he could have been telling the truth. But even if he was lying or exaggerating, it would be understandable under the circumstances. I’m less inclined to believe Jesus said ‘three days and three nights’ when what He meant was ‘three days’. I for one have never said ‘three nights’ when I meant ‘two nights’. Something to think about, anyway.
Verse 12 doesn't say the slave said he hadn't - it says he hadn't: "And when he had eaten them his spirit returned, and he was refreshed: for he had not eaten bread, nor drunk water three days, and three nights."