The horseleach hath two daughters, crying, Give, give. There are three things that are never satisfied, yea, four things say not, It is enough:
Proverbs can be dark sayings (Pr 1:6). They are often not plain (John 16:25,29). They are to make you think, enjoy the interpretative process, and remember the lesson.
We know the lesson of this proverb by its words and context. Its words introduce things in life that are never satisfied or contented, four things that always want more. Its context lists the four things - the grave, the barren womb, dry ground, and an out-of-control fire. So we know the lesson is referring to things that are never satiated, full, or pacified.
What is a horseleach? Other than the name for a horse doctor, farrier, or veterinarian surgeon, it is the name of a blood-sucking leech, which has the reputation of an insatiable thirst for the blood of its victim. The Oxford English Dictionary states,
Horseleach. An aquatic sucking worm differing from the common leech in its larger size, and in the formation of the jaws. A rapacious, insatiable person.
Agur is not teaching veterinary science, so we understand him to be introducing never-satisfied, always-wanting-more, and never-content persons and things. He is starting one of his lists of four things, which occupy much of this chapter (Pr 30:11-31). The bloodsucker is a great introduction, for we still use it to describe insatiable people.
What are the two daughters? They are more things or people of the same character, which the Bible indicates by references to children (Ezek 16:44-45; Matt 23:31; John 8:44; Acts 7:51). The two means no more than does the three, when he plans to list four. Unless the noun or context requires its importance, the number is irrelevant (II Kgs 9:32).
Agur will list in the next verse four things that are never satisfied, four things that never say, It is enough. These observations from nature are to teach us about each one and to recognize by the lesson that there are people and things that can never be satisfied. But we will consider them when we come to that text. Until then, understand the category.
Contentment is a virtue contrary to these things (I Tim 6:6; Heb 13:5). Paul learned to say he was full, even when hungry (Phil 4:11-13). Implacability, or never being satisfied, is a forgotten sin of the New Testament (Rom 1:31). The only insatiable appetite we should have is for spiritual blessings (Gen 32:26; Mat 5:6; Rom 9:1-3; 10:1; I Cor 12:31).
Saints know the flesh has many lustful daughters with insatiable greed, which we are to mortify to the glory of God (Job 15:16; Eph 4:17-19; Col 3:5-7). Silver will not satisfy the man who allows himself to desire it, until it has destroyed him (Eccl 5:10; I Tim 6:7•10). Women will not satisfy the man who craves them, until they destroy him (Judges 16:16-17; I Kings 11:1-11; Eccl 7:26-28).
Dear reader, if the LORD is your Portion, He will cure your cravings and bring contentment and satisfaction like nothing else in the whole world (Ps 73:25-26; Phil 3:8).