1 Thes. 3:6-10 (ESV)
But now that Timothy has come to us from you, and has brought us the good news of your faith and love and reported that you always remember us kindly and long to see us, as we long to see you—  for this reason, brothers, in all our distress and affliction we have been comforted about you through your faith.  For now we live, if you are standing fast in the Lord.  For what thanksgiving can we return to God for you, for all the joy that we feel for your sake before our God,  as we pray most earnestly night and day that we may see you face to face and supply what is lacking in your faith?
Supply what is lacking in your faith? One wonders what that is. I suppose if I was Pentecostal I might think it was the lack of tongues speaking. I’m not Pentecostal. I might think it was baptism of the holy spirit or something If I was Baptist. But it seems to me that it wasn’t that their faith was weak. As the Thessalonians have a faith that has withstood afflictions that would put most American Christians to shame. They have faith. They have strong faith. It seems to me though that Paul might not have been done teaching them the faith. That is he wasn’t done giving them the doctrinal content that would solidify them even more. Maybe that reflects a Lutheran bias. So be it.