Messiah’s past work…for your present healing.
Notice how Isaiah wrote in the past tense even though this prophecy would not be fulfilled until hundreds of years later. How great our God is…to know the future before it becomes a reality to us.
[(NIV) Isaiah 46:10 “I make known the end from the beginning, from ancient times, what is still to come. I say: My purpose will stand, and I will do all that I please.” (NIV) Isaiah 4611b “What I have said, that will I bring about; what I have planned, that will I do.”]

(NASB) Isaiah 53:5 “But He was pierced through for our transgressions,
He was crushed for our iniquities;
The chastening for our well-being fell upon Him,
And by His scourging we are healed.”

“pierced through”, “crushed” – words written in the past tense…it was a done deal from God’s point of view.
“chastening”, “scourging” – words in the present tense…what happened in the past is still effective for you.

Why did the Lord Jesus Christ (Messiah) receive “chastening” and “scourging”?  For you!

For your transgressions (The violation of a law, command or duty)!

For your iniquities (wickedness, a grossly immoral act, sin)!

For your “well-being”!
For your “healing”!

Christ Jesus’ sacrifice: To provide salvation from God’s wrath toward sins…your sins.
Christ Jesus’ sacrifice: To provide salvation for you to be in God’s presence in eternity.

Your salvation has nothing to do with anything you have done or can do. Your salvation is all in what the Lord Jesus Christ has done on the cross and in His resurrection. Your salvation is dependent on what He is continuing to do through His Holy Spirit…by drawing you to the living God for your salvation.

Glory and honor and praise belong to the Living God Who has provided forgiveness for our transgressions, for our well-being and our healing.