On the identity of the prophets,
there are two possibilities: the prophets of the Old Testament (people like Isaiah, Jeremiah, Amos, Zechariah) or the prophets of the New Testament (people like Agabus, Acts 21:10; see also 1 Corinthians 12:28; Ephesians 3:5; Ephesians 4:11). Of these two options, Peter’s reference must be to the former since at the end of 1 Peter 1:11 he mentions that they were predicting the sufferings of Christ and the glories that followed (and hence of necessity lived before Christ). The New Testament prophets lived and spoke after those sufferings and so could no longer predict them.
10 Concerning this salvation, the prophets who prophesied about the grace that was to be yours searched and inquired carefully,