The short but urgent admonitions in this verse may be explained by the knowledge which the father has of the temptations to which youth is exposed and the liability of youth to fall into them, as well as by the fact that Instruction, or Wisdom, is the bestower of life.
This latter conviction is the reason why he urges "taking fast hold" of Wisdom. The tenacious grasp with which the shipwrecked sinking sailor lays hold on any spar or plank floating near will illustrate the kind of grasp with which Wisdom is to be held.
It is no less a virtue to keep and hold fast a good thing than to get it at the first beginning (Muffet). Instruction (musar), usually of a disciplinary nature (see Proverbs 1:3), here more particularly the instruction of the father, but in a wider sense wisdom generally, with which it is synonymous, as appears from the feminine, "let her not go, keep her," musar being masculine; or the feminines may refer back to "Wisdom" in Proverbs 4:11.
So Mercerus and Buxtorf. For she is thy life (ki hi khayyeka); i.e. she brings life to thee. Wisdom is represented as the bestower of long life, in Proverbs 3:2, Proverbs 3:16, Proverbs 3:18. Just in proportion as Wisdom is retained and guarded, so is life secured, and so far as the hold upon her is lost, so are the hopes of life diminished.
Life depends upon the observance of her precepts.