In an incredible display of love for the church at Thessalonica Paul said that     he couldn't endure it anymore unless he knew their welfare.  Paul gives us a good idea of what it means to love the church in this passage.  Paul had more concern for their spiritual and eternal well-being than even their physical and emotional needs.  Paul showed his love by praying for them night and day that their love and faith might grow and increase.  He echoed what he mentioned at the end of chapter two that when the Lord comes for His church they would be a passion to him by their blameless and holiness before God.