What does 1 Peter 1:10 mean?
Verse 10 has to be read and understood together with verse 11. Peter has just finished referring to the salvation of those who trust in Christ. This salvation is available only by God's grace through the faith of those who believe (Ephesians 2:8–9).This idea of salvation by God's grace was not new to Peter, or the other apostles. It had been described and predicted by Israel's prophets generations before, in the Old Testament Scriptures. Peter now reveals to us something about those prophets. Though these men were deeply respected by his readers, they need to realize that these prophets themselves did not fully understand—yet—the message God had given them.
And these ancient writers knew full well that they were missing part of the puzzle. The prophets, inspired by the Holy Spirit of God, wrote of God's coming grace for those of Peter's time (and ours). Then, these prophets searched and asked questions, hoping to understand what they had written. Verse 11 describes specifically what they wanted to know.