God disciplines them

Hebrews 12:3-11 (ESV)

^3  Consider him who endured from sinners such hostility against himself, so that you may not grow weary or fainthearted.

^4  In your struggle against sin you have not yet resisted to the point of shedding your blood.

^5  And have you forgotten the exhortation that addresses you as sons? “My son, do not regard lightly the discipline of the Lord, nor be weary when reproved by him. 

^6  For the Lord disciplines the one he loves, and chastises every son whom he receives.” 

^7  It is for discipline that you have to endure. God is treating you as sons. For what son is there whom his father does not discipline?

^8  If you are left without discipline, in which all have participated, then you are illegitimate children and not sons.

^9  Besides this, we have had earthly fathers who disciplined us and we respected them. Shall we not much more be subject to the Father of spirits and live?

^10  For they disciplined us for a short time as it seemed best to them, but he disciplines us for our good, that we may share his holiness.

^11  For the moment all discipline seems painful rather than pleasant, but later it yields the peaceful fruit of righteousness to those who have been trained by it.