Jamieson, Fausset and Brown on 1 Thessalonians 5:13

13. very highly--Greek, "exceeding abundantly."

for their work's sake--The high nature of their work alone, the furtherance of your salvation and of the kingdom of Christ, should be a sufficient motive to claim your reverential love. At the same time, the word "work," teaches ministers that, while claiming the reverence due to their office, it is not a sinecure, but a "work"; compare "labor" (even to weariness: so the Greek), 1Th 5:12.

be at peace among yourselves--The "and" is not in the original. Let there not only be peace between ministers and their flocks, but also no party rivalries among yourselves, one contending in behalf of some one favorite minister, another in behalf of another (Mr 9:50; 1Co 1:12; 4:6).