In the twilight, in the evening, in the {c} black and dark night:

(c) He shows that there was almost no one so impudent that they were not afraid to be seen, their consciences accusing them and causing them to seek the night to cover their filthiness.

King James Translators' Notes

in the evening: Heb. in the evening of days

Jamieson-Fausset-Brown Bible Commentary

9. The time, twilight, ending in darkness.

black . night-literally, "pupil," or, "eye," that is, middle of night.

Matthew Henry's Concise Commentary

7:6-27 Here is an affecting example of the danger of youthful lusts. It is a history or a parable of the most instructive kind. Will any one dare to venture on temptations that lead to impurity, after Solomon has set before his eyes in so lively and plain a manner, the danger of even going near them? Then is he as the man who would dance on the edge of a lofty rock, when he has just seen another fall headlong from the same place. The misery of self-ruined sinners began in disregard to God's blessed commands. We ought daily to pray that we may be kept from running into temptation, else we invite the enemies of our souls to spread snares for us. Ever avoid the neighbourhood of vice. Beware of sins which are said to be pleasant sins. They are the more dangerous, because they most easily gain the heart, and close it against repentance. Do nothing till thou hast well considered the end of it. Were a man to live as long as Methuselah, and to spend all his days in the highest delights sin can offer, one hour of the anguish and tribulation that must follow, would far outweigh them.