What does it mean that the Lord adds 'such as should be saved'?

This phrase underscores the sovereign grace of God in the salvation process, highlighting that God’s choice precedes human action. Those who are added to the church are not random but are those the Father has eternally loved and chosen in Christ. This reflects the assurance for believers that their salvation is secured by God's purpose and plan, and it reinforces the believers' responsibility to preach the gospel, knowing that God will fulfill His promise of salvation for His chosen ones.