Otherwise, He would have needed to suffer often since the foundation of the world; but now once at the consummation of the ages He has been manifested to put away sin by the sacrifice of Himself.Hebrews 9:26(NASB)
We are reminded in the previous verses that the old covenant required Israel's high priest to enter the holy place, year by year on the day of Atonement, to make their oft-repeated sacrifice to the Lord for the sins of God's people. And so their sins were covered for one more year.
Like all humanity, the high priest was a sinner himself in need of a Saviour, so (unlike the Lord Jesus) he could not come to offer his own blood on the alter. He offered the blood of animals that would simply cover his own sin and the sin of the people for a little longer. This annual sacrifice continued until the full, final, perfect sacrifice in the person of the Lord Jesus Christ was offered as the atoning sacrifice for the sin of the whole world - that day at Calvary - on that pivotal point in the history of humanity.
The atoning sacrifice of the old covenant, where the blood of bulls and goats was offered, was repeated year after year, covering sin for the people of Israel for just one more year. However, the glorious sacrifice of the new covenant was made through the sinless blood of the eternal Son of God (the perfect Son of Man) Who made one, single offering of Himself through the shedding of His own blood on the Cross, putting away forever the sin of all sinners: "Otherwise," as we read in Hebrews, "He would have needed to suffer often since the foundation of the world."
Christ suffered once and only once. Christ suffered once for all on the Cross, and Christ's 'once-for-all' sacrifice was sufficient to pay the full and final price for the sin of the whole world so that whosoever believes on HIM should not perish but have everlasting life.
The Lord Jesus appeared as foretold by so many of God's anointed prophets at the consummation of the age of Israel. Christ was manifested in the flesh at God's appointed time, at the closing of the old covenant of Law, which had demonstrated the imperfections of humanity and man's inability to reach God's perfect standard, and which He used as a schoolmaster to point us to Christ as the one and only eternal sacrifice for sin.
The Old Testament saints looked forward to that pivotal point in history when the promised Seed of the woman, the Messiah of Israel, would be born into the human race as Emmanuel, God with us. And we who live in the dispensation of grace, look back with grateful thanks to that day on Calvary's hill, when God in the person of Jesus Christ was manifest in the flesh to put away sin forever - by the sacrifice of Himself.
Heavenly Father, thank You for Jesus. Thank You that by His once and forever offering of Himself on the Cross, He paid the full and final price for sin so that whoever trusts in Him for salvation will not perish but have everlasting life. Bring many into the kingdom of Your dear Son. In His name I pray, AMEN.