The fear of the LORD is the beginning of wisdom: and the knowledge of the holy is understanding.
The fear of the Lord (is) the beginning of wisdom - repeated from Proverbs 1:7. Having furnished her table, Wisdom shows the viands first, the fear of the Lord.
And the knowledge of the Holy (is) understanding. "The knowledge of the Holy" is the knowledge of all that is involved in hallowing God's name; knowing experimentally all that tends to our sanctifying the Lord in our hearts and in life. The parallelism to "The fear of the Lord" favours our taking the Hebrew Kedoshim for "the holy God," (Proverbs 30:3; note, Hosea 11:12, margin.) The same plural is used as the epithet of God in Joshua 24:19. Its plural form, like 'Elohiym (H430), implies the Trinity (cf. Leviticus 11:44; Leviticus 19:2).