For what thanks are we able to repay to God concerning you on the basis of all the joy which we rejoice because of you before our God, night and day beyond measure supplicating for the purpose of seeing your face and put in order the lacking of your faith? 1 Thessalonians 3:9–10.
Paul earnestly desired to teach the Thessalonians more about the faith, for he had labored among them for only three weeks. Within that brief span he could not fully expound faith in Christ and the new relationship with God; therefore, he longed to impart the additional instruction needed to establish and strengthen their faith.
Although God did not open the way for Paul to return, his supplication was answered: Timothy and the other saints supplied the doctrinal details Paul had lacked time to expound. The labor of his fellow-workers both established and strengthened the believers, whose faith became known throughout all the region.