What the Bible says -

Romans 6:10  For the death that He died, He died to sin once for all; but the life that He lives, He lives to God.

Hebrews 7:27  ..who does not need daily, as those high priests, to offer up sacrifices, first for His own sins and then for the people’s, for this He did once for all when He offered up Himself.

Hebrews 9:12 ...  Not with the blood of goats and calves, but with His own blood He entered the Most Holy Place once for all, having obtained eternal redemption.

Hebrews 9:26 ... He then would have had to suffer often since the foundation of the world; but now, once at the end of the ages, He has appeared to put away sin by the sacrifice of Himself.

Hebrews 10:10  ....By that will we have been sanctified through the offering of the body of Jesus Christ once for all.