Hebrews 13:18
4 “Pray for us” (he says); “for we trust we have a good conscience among all, willing to live honestly.”
You see that he used these apologies, as writing to persons grieved with him, as to those who turned away, who were disposed as towards a transgressor, not enduring even to hear his name? Inasmuch then as he asked from those who hated him what all others ask from those who love them [their prayers for him], therefore he here introduces this; saying, “We trust that we have a good conscience.” For do not tell me of accusations; our conscience, he says, in nothing hurts us; nor are we conscious to ourselves that we have plotted against you. “For we trust,” he says, “that we have a good conscience among all,” not among the Gentiles only, but also among you. We have done nothing with deceitfulness, nothing with hypocrisy: for it was probable that these [calumnies] were reported respecting him. “For they have been informed concerning you” (it is said) “that you teach apostasy.” Not as an enemy, he means, nor as an adversary I write these things, but as a friend. And this he shows also by what follows.
Source: Homilies on the Epistle to the Hebrews (New Advent)