What does Acts 1:24 mean?

The 120 followers of Jesus have been praying for days. Peter has given direction that they need to find a replacement for Judas Iscariot so the apostles number twelve again. After listing the qualification, two men are proposed: Joseph Barsabbas and Matthias (Acts 1:12–23).

Now the group prays again. God promises that if we pray for wisdom, He will give it to us (James 1:5). God knows the hearts of people where we only see on the surface (1 Samuel 16:7; Mark 2:8, 10:17–31; John 2:23–25). God knows who will make the best apostle because He already determined what work each man would do (Ephesians 2:10). Praying for potential leaders becomes a valued tradition in the church for roles like evangelists (Acts 13:2) and church elders (Acts 14:23). Even Jesus prayed before He picked out the Twelve (Luke 6:12–13).

Literally, the verse says, "You, Lord, heart-knower of all…" "Heart-knower" is from the unique Greek word kardiognōstēs. God is the only being whose identity and character include the knowledge and understanding of our thoughts, feelings, desires, and intentions. As such, only He can know whether Joseph or Matthias is the right man to replace Judas and take his responsibilities (Acts 1:20). The only other place "heart-knower" is used is in Acts 15:8 when Peter affirms that when it comes to inherent righteousness, Jews are no different than Gentiles.