The writer to the Hebrews conveyed this truth from the Spirit to all Believers:
"By one offering
He has perfected forever
those who are being sanctified," Hebrews 10'14.
Being sanctified is the process of being transformed into the image of Christ. God began sanctifying Jesus' Called-Out Ones into the likeness of His Son right from the day they received Him.
2 Corinthians 3'18 sums up the way the sanctifying happens:
"... we all, with unveiled face,
beholding as in a mirror the glory of the Lord,
are being transformed into the same image from glory to glory,
just as by the Spirit of the Lord".
"Now may the God of peace Himself sanctify you completely;
and may your whole spirit, soul, and body be preserved blameless
at the coming of our Lord Jesus Christ,"
1 Thessalonians 5'23.