Jamieson, Fausset and Brown on Hebrews 13:18

18. Pray for us--Paul usually requests the Church's intercessions for him in closing his Epistles, just as he begins with assuring them of his having them at heart in his prayers (but in this Epistle not till He 13:20, 21), Ro 15:30. "Us," includes both himself and his companions; he passes to himself alone, He 13:19.

we trust we have a good conscience--in spite of your former jealousies, and the charges of my Jewish enemies at Jerusalem, which have been the occasion of my imprisonment at Rome. In refutation of the Jews' aspersions, he asserts in the same language as here his own conscientiousness before God and man, Ac 23:1-3; 24:16, 20, 21 (wherein he virtually implies that his reply to Ananias was not sinful impatience; for, indeed, it was a prophecy which he was inspired at the moment to utter, and which was fulfilled soon after).

we trust--Greek, "we are persuaded," in the oldest manuscripts. Good conscience produces confidence, where the Holy Spirit rules the conscience (Ro 9:1).

honestly--"in a good way." The same Greek word as "good conscience." Literally, "rightly," "becomingly."