Jamieson, Fausset and Brown on 1 Timothy 5:17

17. The transition from the widow presbyteresses (1Ti 5:9) to the presbyters here, is natural.

rule well--literally, "preside well," with wisdom, ability, and loving faithfulness, over the flock assigned to them.

be counted worthy of double honour--that is, the honor which is expressed by gifts (1Ti 5:3, 18) and otherwise. If a presbyter as such, in virtue of his office, is already worthy of honor, he who rules well is doubly so [Wiesinger] (1Co 9:14; Ga 6:6; 1Th 5:12). Not literally that a presbyter who rules well should get double the salary of one who does not rule well [Alford], or of a presbyteress widow, or of the deacons [Chrysostom]. "Double" is used for large in general (Re 18:6).

specially they who labour in the word and doctrine--Greek, "teaching"; preaching of the word, and instruction, catechetical or otherwise. This implies that of the ruling presbyters there were two kinds, those who labored in the word and teaching, and those who did not. Lay presbyters, so called merely because of their age, have no place here; for both classes mentioned here alike are ruling presbyters. A college of presbyters is implied as existing in each large congregation. As in 1Ti 3:1-16 their qualifications are spoken of, so here the acknowledgments due to them for their services.