What does it mean that the leech has two daughters (Proverbs 30:15)?

Leeches are abundant in Palestine, and the horseleech may simply refer to a large species that would settle on a horse's foot if placed in the water where they abound. A horse has been known, in drinking, to get a leech into its mouth, which immediately began to suck its blood. The leech is used symbolically of a rapacious person, who is never satisfied, graphically delineated by the leech's two daughters, who say, 'Give, give.' Prov. 30:15.

The proverb in the form of a command in verse 10 is isolated from the trend of thought in this chapter. The first quatrain comes next in verses 11-14. Four times the word generation is used, describing the classes of people frequently mentioned in the preceding chapters of proverbs. Then follow four things which are insatiable. The climax is reached gradually. The horseleach (or vampire) has two daughters by name of "Give." Even so is the poor heart of man; and there are three and four things of the same character; the unseen regions into which disembodied spirits are going day after day, year after year; the barren womb; the earth upon which rain descends yet is never filled with water, and the fourth thing, the fire, which never saith, it is enough, which consumes till nothing is left. These unsatiable things mentioned are symbolical of the condition of the natural man, always taking in yet always, restless and never satisfied.

"The leech hath two daughters: Give, give. There are three things never satisfied four which, say not, 'It is enough: Sheol, and the barren womb; the earth which is not filled with water, and the fire which saith not, It is enough" (New Trans.).

Is there not here the implied lesson that man by nature resembles a leech, a parasite, always ready to draw from a supply not really his own? So Israel in the wilderness, having been shown wonderful grace from God, only responded with continual dissatisfaction and murmuring. "Give, give" was her language, with little spirit of thankfulness.

And this, though there can hardly be anything in the universe more difficult to satisfy than the human heart; for in it live the horseleech's two daughters, incessantly crying, Give, give. It is more insatiable than the grave: the maw of the sea and the yawning earthquake are less greedy. Apicius killed himself because he had only eighty thousand pounds left; Ahab had all Israel, but sickened for Naboth's vineyard; a "little corporal," having all the best parts of Europe, must also try and rob the Muscovite of his frozen plains; "a little stooping man," having conquered the whole world, sits down and weeps for another to conquer. "To be equal with God" would not satisfy the Antichrist: he will exalt himself "above all that is called God." Though "Ambition has one heel nailed in hell, She doth stretch her fingers to touch the heavens."

Solomon says, "All the rivers run into the sea, yet the sea is not full" (Ecc. 1:7). The sea is the human heart. If you could direct into those discontented hearts every river of earthly pleasure, they would still remain unfilled, unsatisfied. Men hunt for satisfaction where it never can be found. An iceberg yields no heat, salt no sweetness, and wine cannot be pressed from turnips. Man's heart was made for God, and only God, in Christ, can fill and satisfy it. Riches, fame, pleasure, all fail to bring contentment to the heart.

It is impossible for the intelligent creature, placed originally in happy relationship with God, to find permanent satisfaction in anything beneath him, whatever resources may be apparently at his disposal. This is why man in his fallen condition has hunger in his heart, which nothing seems able to appease. The world proposes to cure this painful malady, but the very number of its panaceas witnesses against its proud pretensions, and those who have tried them bitterly complain that they have spent their money for that which is not bread, and their labour for that which satisfieth not. Solomon asks, “Who has woe? Who has sorrow? Who has contentions? Who has babbling? Who has wounds without cause? Who has redness of eyes?” And he supplies the answer: “They that tarry long at the wine; they that go to seek mixed wine.” And he adds, “Look not thou upon the wine when it is red, when it gives his colour in the cup, when it moveth itself aright. At the last it biteth like a serpent, and stingeth like an adder” (Prov. 23:29-32). And wine is but a figure of the best of earthly joys, which never satisfy, and are only vanity and vexation of spirit.