Adam Clarke on 1 Corinthians 15:28

The Son also himself be subject - When the administration of the kingdom of grace is finally closed; when there shall be no longer any state of probation, and consequently no longer need of a distinction between the kingdom of grace and the kingdom of glory; then the Son, as being man and Messiah, shall cease to exercise any distinct dominion and God be all in all: there remaining no longer any distinction in the persons of the glorious Trinity, as acting any distinct or separate parts in either the kingdom of grace, or the kingdom of glory, and so the one infinite essence shall appear undivided and eternal. And yet, as there appears to be a personality essentially in the infinite Godhead, that personality must exist eternally; but how this shall be we can neither tell nor know till that time comes in which we shall See Him as He Is. 1Jn 3:2.