We always thank God for all of you and continually mention you in our prayers. We remember before our God and Father your work produced by faith, your labor prompted by love, and your endurance inspired by hope in our Lord Jesus Christ. (1 Thessalonians 1:2-3, NIV)
The Pauline emphasis on the triad of faith, hope, and love is better known from 1 Corinthians 13, but here we see it in what is considered by many to be his earliest letter.
Faith produces work.
Love prompts labor.
Hope inspires endurance.
These are the marks of the church for which Paul is thankful. The fact that the church has faith, love, and hope is indicated not by its mission statement or preaching, but by its work, labor, and endurance.
This list also bridges some of the supposed divide between Paul and James. We see here as well as in James the linkage of faith and works.
And so, these outward things become for us signs of the inward character. A church that has faith produces works. A church that loves labors. A church that has hope endures through difficulty and trials.
For these marks Paul thanked God for the Thessalonian Christians.