John Gill Commentary Proverbs 3:12

"For whom Jehovah loveth he reproveth; Even as a father the son in whom he delighteth." — Proverbs 3:12 (ASV)

For whom the Lord loves he corrects
This is a reason why the children of God should not despise corrections, nor be weary of them; since they spring from love, are given in love, nor is there any abatement of it in them: when the Lord chastens and corrects, he does not take away his lovingkindness from them; yes, it is because he loves them that therefore he thus deals with them; wherefore they ought to be patiently borne, and kindly taken by them;

even as a father the son [in whom] he delights ;
as a father chastens and corrects his son, whom he dearly loves, and has the greatest pleasure in, so the Lord chastens and corrects his people; see (Deuteronomy 8:5) . There is such a relation subsisting between them as that of father and son, which flows from the inexpressible love of God to them; and which is a love of complacency and delight in them, and is invariable and unchangeable, and continues the same under all their afflictions; as appears by what he does for them in them, and by the issue of them; he knows their souls in adversity, and chooses them in the furnace of affliction; he pays love visits to them, and comforts them under all their tribulation; he sympathizes with them, and supports them; he makes their bed in their affliction, and delivers out of it, or takes them to himself: the issue is always his own glory, and their good.