Justified solely by His Death !
That those Christ died for are Justified solely by His death, apart from any obedience from them He died for, is a Truth taught in scripture and is part of the Gospel of God which Paul Preached Rom 1:1. One such scripture is Rom 5:19, this verse teaches that by the obedience of ONE, that One being Jesus Christ, That Obedience being His Death Phil 2:8;Heb 2:9, that many shall be made Righteous [ That's Saved] Now what is Plainer than that ? To be declared Righteous is Justification and it is Salvation which is effected solely by Christ's Obedience which is His Death.
Now the OT counterpart of the same Gospel Truth is here Isa 53:11
11 He shall see of the travail of his soul, and shall be satisfied: by his knowledge shall my righteous servant justify many; for he shall bear their iniquities.
They are being Justified or accounted Righteous here as a result of His Knowledge and Bearing their sins, which is the same as His Obedience of One in Rom 5:19b
19 For as by one man's disobedience many were made sinners, so by the obedience of one shall many be made righteous.
Now some will say that it says in Isa 53:11, by His Knowledge shall my Righteous Servant Justify many, but that matters not, nor does it detract from the plain stated truth, for its not by the sinners knowledge that He shall Justify many, but by His Own Knowledge He shall do it. Now since this verse is the OT counterpart to Rom 5:19, His Knowledge in Isa 53:11 is His experiential knowledge in that by the things He suffered, He Learned Obedience Heb 5:8
8 Though he were a Son, yet learned he obedience by the things which he suffered;
The word learned here is the greek word manthanō:
I.to learn, be apprised
A.
to increase one's knowledge, to be increased in knowledge
B.
to hear, be informed
C.
to learn by use and practice
i.
to be in the habit of, accustomed to
Also the word for obedience here in Heb 5:8 is the same one in Rom 5:19.
What He learned was Knowledge. His being acquainted with grief was learned knowledge as Per Isa 53:3
He is despised and rejected of men; a man of sorrows, and acquainted with grief: and we hid as it were our faces from him; he was despised, and we esteemed him not.
The word acquainted, the Hebrew yada is the root word for Knowledge in Isa 53:11 and it does mean to know by experience.
Now all this goes to show the Gospel Truth, that by His Death alone, all those He died for are accounted Righteous before God's Law and Justice, BEFORE THEY BELIEVE ! In fact before they are born sinners. To deny this is to deny the Gospel of God, it Deny's the Death of Christ, which leaves one without any other hope of Salvation !