Jamieson, Fausset and Brown on 2 Thessalonians 1:3

3. We are bound--Greek, "We owe it as a debt" (2Th 2:13). They had prayed for the Thessalonians (1Th 3:12) that they might "increase and abound in love"; their prayer having been heard, it is a small but a bounden return for them to make, to thank God for it. Thus, Paul and his fellow missionaries practice what they preach (1Th 5:18). In 1Th 1:3, their thanksgiving was for the Thessalonians' faith, love, and patience"; here, for their exceeding growth in faith, and for their charity abounding. "We are bound" expresses the duty of thanksgiving from its subjective side as an inward conviction. "As it is meet," from the objective: side as something answering to the state of circumstances [Alford]. Observe the exact correspondence of the prayer (1Th 3:12, "The Lord make you to abound in love") and the answer, "The love of every one of you all toward each other aboundeth" (compare 1Th 4:10).

meet--right.