But now, once at the end of the ages, he has appeared to put away sin by the sacrifice of himself. … so Christ was offered once to bear the sins of many. To those who eagerly wait for him he will appear a second time, apart from sin, for salvation. Hebrews 9:26-28.
The believers of the age of grace will then be taken up to the glory of heaven; at a later time the believing remnant of Israel will enter the blessings of the millennium. Both events are aspects of the forthcoming return of the Lord, and for both of them His sacrifice made once for all time was a pre-requisite.
When the Lord comes, we shall see Him as he is. But the eye of faith can see Christ even now “crowned with glory and honor” in heaven. There He is at present as the forerunner for us (Chapter 2:9; 6:20). What security that affords us for our future!