For what thanks can we render to God again or you,.... They had given thanks to God for them before, for their faith, love, and patience; see 1Th 1:2 and now having received a further account of them, they looked upon themselves bound to give fresh thanks to God for them, for the increase of their faith and love, and for their perseverance, as they did; see 2Th 1:3 since these are gifts of God's grace; but they knew not where to begin, what to render, and when to end: the phrase is much like that in Ps 116:12 "what shall I render unto the Lord", &c.
for all the joy wherewith we joy for your sakes before our God: the joy they had was all joy, perfect and complete in its kind; see Jas 1:2 and it was not for themselves, on their own account, because of any worldly interest or advantage they had therein, but for the sake of these Thessalonians, whose spiritual welfare they rejoiced at: nor was their joy of a carnal nature, but spiritual; it was a joy in the Holy Ghost, and which was hearty and sincere: it was "before God our" God, their covenant God and Father; it was in his sight and presence, who sees and knows all things, all actions, and the principles of them.