Galatians 4:4

the fulness of the time--namely, "the time appointed by the Father" (Gal 4:2). Compare Note, see on Eph 1:10; Luk 1:57; Act 2:1; Eze 5:2. "The Church has its own ages" [BENGEL]. God does nothing prematurely, but, foreseeing the end from the beginning, waits till all is ripe for the execution of His purpose. Had Christ come directly after the fall, the enormity and deadly fruits of sin would not have been realized fully by man, so as to feel his desperate state and need of a Saviour. Sin was fully developed. Man's inability to save himself by obedience to the law, whether that of Moses, or that of conscience, was completely manifested; all the prophecies of various ages found their common center in this particular time: and Providence, by various arrangements in the social and political, as well as the moral world, had fully prepared the way for the coming Redeemer. God often permits physical evil long before he teaches the remedy. The smallpox had for long committed its ravages before inoculation, and then vaccination, was discovered. It was essential to the honor of God's law to permit evil long before He revealed the full remedy. Compare "the set time" (Psa 102:13). was come--Greek, "came." sent forth--Greek, "sent forth out of heaven from Himself" [ALFORD and BENGEL]. The same verb is used of the Father's sending forth the Spirit (Gal 4:6). So in Act 7:12. Compare with this verse, Joh 8:42; Isa 48:16. his--emphatical. "His own Son.

— Jamieson-Fausset-Brown Commentary (public domain)