John Gill Commentary 1 Thessalonians 3:7

"for this cause, brethren, we were comforted over you in all our distress and affliction through your faith:" — 1 Thessalonians 3:7 (ASV)

Therefore, brethren, we were comforted over, you
Or "in you", as the Vulgate Latin version; or "from you", as the Arabic; or "by you", as the Syriac; or "for you", as the Ethiopic; that is, on account of them, either by what they had heard was in them, or had heard from them. This gave abundant consolation

in all our affliction and distress :
which they met with at Corinth, where the apostle laboured with his own hands, and ministered to his own, and the necessities of others, and was greatly opposed, reproached, and persecuted; see (Acts 18:3Acts 18:6Acts 18:9Acts 18:10Acts 18:12) , but the news of the good estate and condition the Thessalonians were in, was a great relief and comfort to him, particularly their faith:

by your faith :
by the report of it, that it grew exceedingly, and that they walked in the truth; see (1 John 5:4) . The Alexandrian copy reads, "in all your distress and affliction, and by your faith."