Regeneration — New life imparted
It’s the internal work of the Holy Spirit.
God gives us a new heart and makes us spiritually alive.
Term often associated with being "born again."
“...by the washing of regeneration and renewal of the Holy Spirit.” – Titus 3:5
Justification — Legal standing declared
It’s the external declaration by God as judge.
God declares us righteous because of Christ’s righteousness.
This happens by faith, not by works.
“Therefore, since we have been justified by faith, we have peace with God…”– Romans 5:1
At conversion, regeneration is what God does in us (new birth), Justification is what God declares over us (right standing). They're distinct, but inseparable–like two sides of a coin. You can think of them as two simultaneous dimensions of salvation: one experiential, one positional.