The word 'tetelestai' was used in the same markets to signify the transaction is finished, done. It was also written on the prisoner's penalty page to signify the penalty was paid in full when they were released from imprisonment.
Salvation is synonymous with Justification, in my calculus, because The Bible aligns us as at enmity with God, then we are in need of making restitution/getting right with God somehow, if possible. [I will spare readers my long-winded explanation of getting right with God.]
Jesus made that restitution on the Cross. So, believing in Him as Redeemer and Lord, we are justified, marked clean from guilt toward God. It is because of this 'cleansing' that God then enters the spirit of the 'being born from above'.
Only God is Righteous, so if we are to do works of righteousness we must have His life in us to carry it forward. That's why I'm fond of connecting being born from above with being then raised up in the Way that we should go, as members in God's adopted family.
The most astonishing contrast between the Old Covenant and the New Covenant Jesus instituted is the reality that God justifies us then puts His Life in us! we are literally reborn in a moment, the moment we believe He is Messiah and Lord, our Lord. ... And lest we forget, no man can take us out of the two hands of God. That no man includes me, even I cannot take me out of His hands. The Promises of God are ALWAYS fulfilled. He spoke worlds into existence. He can speak my security for everlasting.
That the atonement of Christ was substitutionary, with Him taking responsibility for what we did wrong, and paying the price Divine justice requires for our sins to be forgiven, on His account. But why must it be limited only to those who appropriate it by redemptive faith?
Surely it does not impugn the character or ability of God to provide grace to all, and allow the lost to reject it. The wedding feast was prepared for all, but not all responded to the call to come, (Mt. 22:1-14) and grace can be received in vain, (1Co. 15:2; 2Co. 6:1; Heb. 6:4-8) though as with God's word, it will accomplish His purposes. In which grace is given, and when rejected it justifies God as gracious and condemns man as wicked, and God judges man based upon the light and grace given.
Yet it is hardly tenable to believe that every NT convert understood theological nature of the atonement, but they did believe that Christ died for our sins and that he was buried, and that he rose again the third day, (1 Corinthians 15:3-4) and that repentance and remission of sins in his name (Luke 24:47) is offered to all who believe with effectual faith. (Rm. 10:9,10; Heb. 6:9,10)
It is obvious the RC position finds fault with penal substitution as an understanding of the atonement, probably most importantly because it negates the need for ongoing propitiation for sin in the mass.
More specifically, which is due to the unScriptural literalistic rendering,of the Lord's Supper into "the same sacrifice with that of the cross...a sacrifice of propitiation, by which God is appeased and rendered propitious,. (The Catechism of the Council of Trent, Published by Command of Pope Pius the Fifth (New York: Christian Press, 1905), p. 175) with Jesus continually sacrificing Himself thru the hands of men uniquely ordained as "priests" - unseen in the NT church - who have God obeying them to become flesh and blood - which no NT clergy seen doing - and is eaten in order to obtain spiritual life - which is nowhere the means of obtaining spiritual life.