9:10 / Verse 10 is a key statement for understanding verses 7–12. Holy One is literally the plural (of majesty) as in 30:3b. Knowledge of the Holy One is a definition of fear of the Lord. As always, knowledge is practical, active, and reverent.
9:10 Once again we are reminded that the starting point for all true wisdom is in the fear of the Lord. “To know the Deity is what knowledge means” (Moffatt). Because he knows the Holy, a true believer can see more on his knees than others can see on their tiptoes.
The Holy One (plural) may be the plural of majesty, excellence, and comprehensiveness, or it may modify Elohim (understood), a plural word for God.
9:10The fear of the Lord. Together with 1:7 (see note), this verse stands as the grounding and thematic statement for all of the appeals to wisdom throughout 1:1–9:18.
9:10 The fear of the Lord. See 1:7 and note; “The Wisdom and Will of God” at Dan. 2:20.
Holy One. Lit. “holy ones” or “saints.” The translation here is based on the parallel with “the Lord” in the previous line (cf. 30:3, where the same plural form is used).
 MacDonald, W. (1995). Believer’s Bible Commentary: Old and New Testaments. (A. Farstad, Ed.) (p. 813). Nashville: Thomas Nelson.
 Sproul, R. C. (Ed.). (2005). The Reformation Study Bible: English Standard Version (p. 886). Orlando, FL; Lake Mary, FL: Ligonier Ministries.