Niddah 17 - All is Predestined, Except Being a Good Person
Engaging in marital relations while it is light is considered vulgar. There are exceptions to this rule, such when one has no other time or is too tired at night. A scholar may cover his bed with a cloak.
What is the source for general rule? Rabbi Yochanan said, from the book of Job, "Likewise the night that declared: A man has been conceived" - night is given for conception, but not day. But Resh Lakish derives it from Proverbs, "One who degrades his way..." and "way" is an euphemism for marital relations. According to Resh Lakish, "night that declared" means something different: there is an angel called "Night," or "Laila." That angel takes the drop from which the child will be conceived, places it before the Holy One Blessed is He, and asks, "Master of the Universe! This drop, what is its destiny? Mighty or weak; intelligent or foolish; wealthy or poor?" However, he does not ask, "Wicked or righteous?" This agrees with the lesson that Rav Chanina derived from the phrase, " And now, Israel, what does God want of you? Only that you remain in awe of God your Lord, so that you will follow all His paths ..."
One should not cohabit in the presence of other living beings. Rabbi Yehudah asked, "Even mice?" Shmuel answered him, "Smart one! I only meant a certain family who engage in relations in the presence of their slaves and slave-women." And what was the family's justification? - Since the Torah said, "Stay here by yourself with the donkey," some people are likened to a donkey. Nevertheless, Abaye would chase away the flies, and Rava - the gnats.
Art: Willem Van Aelst - Still Life with Mouse and Candle