Musar for Nedarim 40:1
בניך יפיפין ביותר אמרה להן אינו מספר עמי לא בתחלת הלילה ולא בסוף הלילה אלא בחצות הלילה וכשהוא מספר מגלה טפח ומכסה טפח ודומה עליו כמי שכפאו שד
thy children so exceedingly beautiful? She replied: [Because] he [my husband] 'converses' with me neither at the beginning nor at the end of the night, but [only] at midnight; and when he 'converses', he uncovers a handbreadth and covers a hand breadth, and is as though he were compelled by a demon. And when I asked him, What is the reason for this [for choosing midnight], he replied, So that I may not think of another woman,<span class="x" onmousemove="('comment',' At the beginning of the night women are still going about in the streets; at the end, before morning, they are abroad again. ');"><sup>1</sup></span>