Albert Barnes 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)

Another enigma. The four things of Proverbs 30:16 agreed in the common point of insatiableness; the four now mentioned (Proverbs 30:19) agree in this: that they leave no trace behind them.

The way of a man with a maid – The act of sin leaves no outward mark upon the sinners.