The Blood Atonement (Acts 20:28;
Romans 3:25, 5:9;
Ephesians 1:7;
Hebrews 9:12-14).
Act 20:28 (NASB)
“Be on guard for yourselves and for all the flock, among which the Holy Spirit has made you overseers, to shepherd the church of God which He purchased with His own blood.
Rom 3:25
whom God displayed publicly as a propitiation in His blood through faith.
This was to demonstrate His righteousness, because in the forbearance of God He passed over the sins previously committed;
Rom 5:9
Much more then, having now been justified by His blood, we shall be saved from the wrath
of God through Him.
Eph 1:7
In Him we have redemption through His blood, the forgiveness of our trespasses, according to the riches of His grace
Heb 9:12
and not through the blood of goats and calves, but through His own blood, He entered the holy place once for all, [fn]having obtained eternal redemption.
Heb 9:13
For if the blood of goats and bulls and the ashes of a heifer sprinkling those who have been defiled sanctify for the [fn]cleansing of the flesh,
Heb 9:14
how much more will the blood of Christ, who through the eternal Spirit offered Himself without blemish to God, cleanse ]your conscience from dead works to serve the living God?
I am always worried when I see the word "atonement" without a definition, it might either refer to Christ's substitutionary sacrifice, or to an individual's redemption when placed spiritually by God into Christ.
Another verse also sheds light to exactly what was "purchased" by Christ's sacrifice.
2Pe 2:1 (NASB)
But false prophets also arose among the people, just as there will also be false teachers among you, who will secretly introduce destructive heresies, even denying the Master who bought them, bringing swift destruction upon themselves.
This verse makes clear Christ's death purchased more than the church (those called into His kingdom) because it also "purchased" those destined for destruction. He became the propitiation or means of salvation for the whole world, all mankind.