The Greek word for discipline in the New Testament is paideia — the same word the Greeks used for the comprehensive education of a child into full humanity. It covers instruction, correction, and sometimes painful training. When Hebrews 12 says God disciplines every son he receives, it is using a word that would have resonated deeply in the ancient world: a father who refuses to discipline his son is not kind, he is negligent.
The sting of discipline is real. Hebrews doesn't pretend otherwise — "no chastening for the present seemeth to be joyous, but grievous." But the argument is about what it produces: the peaceable fruit of righteousness. You can endure something uncomfortable when you understand what it is building. Discipline without that understanding is just pain; discipline inside a Father-child relationship is formation.
The apostle Paul frames the discipline of the Christian life athletically in 1 Corinthians 9. He buffets his body — literally strikes it under — and brings it into subjection. That is not self-loathing; it is the same logic as an Olympic athlete who treats their training schedule as non-negotiable. You don't have to enjoy every session. You just have to show up because you know what you are training for.
Commentary is from a charismatic Protestant perspective, drawing on KJV text and public-domain sources including Spurgeon, Andrew Murray, and Matthew Henry.