How do we know that the blood of Christ was shed for the elect?

In scriptures like Revelation 5:9, it proclaims that Christ was slain and has redeemed people for God from every tribe and language and nation. This strongly indicates that His sacrificial death was not for everyone universally but particularly for those chosen by God. Additionally, Matthew 1:21 tells us that Jesus will save His people from their sins, affirming that His atoning work is effective for the elect. As seen in Galatians 4:4-5, Christ came at the appointed time to redeem those who were under the law, which points to the intentionality of His sacrifice for a definite group of people.