1 Thessalonians 3:7-10

v7-8: News of a Christian backsliding or giving up the faith altogether, is always discouraging to hear.  However, we should always be encouraged by news of someone standing firm in the Lord and faithful to Him and use this as a reminder to keep going in the ministry God has given us to do.

v9: "When we are most cheerful, we should also be most thankful. We should give thanks for what we rejoice in."  Why?  In order to give the glory to God for the joy and encouragement we have received.

v10: "Those we give thanks for still need to be prayed for" because they remain "in this world of temptation and imperfection" and while they do, will have something lacking in their faith.  This could be truths about God "that are insufficiently known or believed by them" or they are still in the dark about, or the effects of these truths are not being displayed in their lives as much as they ought to be.