Sin was not put away until the Lamb of Sacrifice was slain at Calvary.
Hebrews 9:26 is clear and plain.
Not clear and plain about this issue...
How were the sins of the Old Covenant Saints atoned for?
when Christ appeared as a high priest of the good things that have come, then through the greater and more perfect tent (not made with hands, that is, not of this creation) 12 he entered once for all into the holy places, not by means of the blood of goats and calves but by means of his own blood, thus securing an eternal redemption.
An eternal redemption is timeless.
Heb 10
4 For it is impossible for the blood of bulls and goats to take away sins.
How then is any old testament saint atoned for except through the timeless event of the Cross.
Heb 2:
he helps the offspring of Abraham. 17 Therefore he had to be made like his brothers in every respect, so that he might become a merciful and faithful high priest in the service of God, to make propitiation for the sins of the people.
Jesus is of the eternal Order of Melchizedek without beginning of time nor end of days.