Jamieson, Fausset and Brown on Hebrews 12:7

7. In He 12:7, 8 the need of "chastening" or "discipline" is inculcated; in He 12:9, the duty of those to whom it is administered.

If--The oldest manuscripts read, "With a view to chastening (that is, since God's chastisement is with a view to your chastening, that is, disciplinary amelioration) endure patiently"; so Vulgate. Alford translates it as indicative, not so well, "It is for chastisement that ye are enduring."

dealeth with you--"beareth Himself toward you" in the very act of chastening.

what son is he--"What son is there" even in ordinary life? Much more God as to His sons (Is 48:10; Ac 14:22). The most eminent of God's saints were the most afflicted. God leads them by a way they know not (Is 42:16). We too much look at each trial by itself, instead of taking it in connection with the whole plan of our salvation, as if a traveller were to complain of the steepness and roughness of one turn in the path, without considering that it led him into green pastures, on the direct road to the city of habitation. The New Testament alone uses the Greek term for education (paideia), to express "discipline" or correction, as of a child by a wise father.