What is the meaning of the expression “put to death in the flesh but made alive in the spirit”?

There are several things to note about these words.

Peter places two parallel clauses side by side: put to death in the flesh and made alive in the spirit. The fact that they are parallel impacts how we read these words. Commentaries list remarkably divergent understandings of what Peter means here, often based on missing the fact that these clauses are deliberately parallel.

Put to death and made alive are both passive terms, meaning that Jesus was acted upon both in his dying as well as in his coming alive.

Twice in this sentence we find the word in (suggesting location, i.e., where Jesus died, in his flesh; and where Jesus came alive, in his spirit). We need to know that the Greek grammar allows with equal justification the use of the translation by (suggesting means: by whom or how Jesus died and came alive). The definite article the is absent in the Greek in relation to both phrases.

The term flesh is common in the Old Testament to describe mankind in his fallen, finite, fragile state (Isaiah 40:6, a verse Peter had quoted in 1 Peter 1:24). Peter’s word for spirit is not the common term for the human soul (that’s psyche) but is common in relation to the Holy Spirit. It was the Holy Spirit who propelled and equipped Jesus for his ministry (Luke 4:1, Luke 4:14).

If we translate the first part of the phrase as “put to death by flesh,” the event Peter is describing is very clear to us: Jesus suffered so acutely at the hands of the people of Jerusalem that it cost him his life (Peter’s own words in Acts 2:23). Then the significance of the second part of the phrase (its parallel) comes to light too; what flesh killed, God the Holy Spirit made alive again. We have here, then, a reference to the events of Good Friday and Easter Sunday. Jesus could resume after his resurrection the work evidently terminated by his death.