How do we know that Christ's atonement is particular?

The Bible asserts that Christ died for the sheep, indicating a distinct group for whom He laid down His life (John 10:11). The Scriptures make it clear that His atonement is effective only for those chosen by God, as seen in Matthew 1:21, where it states Jesus will save His people from their sins. This principle is underscored in John 17:9, where Jesus explicitly states that He does not pray for the world, but for those the Father has given Him. This underscores God's particular love and exclusive grace towards His elect, affirming that Christ's death was sufficient and necessary for their salvation and that it successfully secured it.