Is Isaiah 53:5 speaking of physical or spiritual healing?

Answer:

"Surely our griefs He Himself bore, and our sorrows He carried; yet we ourselves esteemed Him stricken, smitten of God, and afflicted. 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. All of us like sheep have gone astray, each of us has turned to his own way; but the LORD has caused the iniquity of us all to fall on Him" (Isaiah 53:4-6).

Notice that throughout the immediate context, the reason the Messiah would suffer was because of our griefs, our transgressions, and our iniquities. For these his sufferings brought about our well-being and healing. Thus, we are talking a spiritual healing of the damage done by us due to our sins.