Beauty sleep

A medical man, who may be called up at any moment, must make sure of his ‘beauty-sleep.’

Source: wiktionary

And would I please to remember that I had roused him up at night, and the quality always made a point of paying four times over for a man's loss of his beauty-sleep. I replied that his loss of beauty-sleep was rather improving to a man of so high complexion; and that I, being none of that quality, must pay half-quality prices; […]

Source: wiktionary

At first he was quite peevish. "What's the idea," he said, "coming and spoiling a man's beauty-sleep? Get out."

Source: wiktionary

But eager as Kate was for her beauty sleep, the light burned late in her room; and long after she had seen Mrs. Murray snugly tucked in for the night, she sat with Ranald's open letter in her hand, reading it till she almost knew it by heart.

Source: wiktionary