A.T. Robertson Commentary Hebrews 12:6

"For whom the Lord loveth he chasteneth, And scourgeth every son whom he receiveth." — Hebrews 12:6 (ASV)

Scourgeth (μαστιγο). Present active indicative of μαστιγοω, old verb from μαστιξ (whip). This is a hard lesson for God's children to learn and to understand. See 5:7 about Jesus.