Matthew Henry Commentary Proverbs 30:18-20

"There are three things which are too wonderful for me, Yea, four which I know not: The way of an eagle in the air; The way of a serpent upon a rock; The way of a ship in the midst of the sea; And the way of a man with a maiden. So is the way of an adulterous woman; She eateth, and wipeth her mouth, And saith, I have done no wickedness." — Proverbs 30:18-20 (ASV)

Four things cannot be fully known. The kingdom of nature is full of marvels. The fourth is a mystery of iniquity: the cursed arts by which a vile seducer gains the affections of a female, and the arts which a vile woman uses to conceal her wickedness.