Hebrews 9:25-28 - Christ was sacrificed once

9:25,26

The Levitical High Priest entered the Most Holy Place every year, it was a repeated exercise. And the Levitical priest entered with the blood of an animal. Jesus entered the real heaven only once, and He did this with His own blood. Jesus suffered once, there was only one crucifixion. His one sacrifice dealt with sin once for all. The cross is referred to as “the culmination of the ages”, or “the climax of history”. God’s purpose has always been that man should live in fellowship with Him. “I will be their God, and they will be my people.” The cross is the key event which enables this purpose to be achieved. 

9:27,28

Men die once, and will then face judgement. That is the destiny of all people without Christ. So Christ also died once, but He did not face judgement. Instead His death paid the price for our sins. He died to take away sin, the sins of many (cf Is 53:12). There is then a reference to the second coming. Jesus will appear a second time, this time to bring salvation. Are we not saved already? Yes, in the sense that everything necessary for our salvation has been done (i.e. the cross and resurrection), but the fulfilment of our salvation will occur only when Christ returns. We die mortal, but will be raised immortal (1 Cor 15:42,43). We will be transformed, there will then no longer be any vestige of sin within us, we will be fully sanctified. “To those who are waiting for Him”, ESV is probably more accurate with “eagerly waiting”.