Isaiah 6:9

9.Then he said, Go, and tell that people. (95) This shows still more clearly how necessary the vision was, that Isaiah might not all at once fail in his course. It was a grievous stumblingblock, that he must endure such obstinacy and rebellion in the people of God, and that not only for a year or two, but for more than sixty years. On this account he needed to be fortified, that he might be like a brazen wall against such stubbornness. The Lord, therefore, merely forewarns Isaiah that he will have to do with obstinate men, on whom he will produce little effect; but that so unusual an occurrence must not lead him to take offense, and lose courage, or yield to the rebellion of men; that, on the contrary, he must proceed with unshaken firmness, and rise superior to temptations of this nature. For God gives him due warning beforehand as to the result; as if he had said, “You will indeed teach without any good effect; but do not regret your teaching, for I enjoin it upon you; and do not refrain from teaching, because it yields no advantage; only obey me, and leave to my disposal all the consequences of your labors. I give you all this information in good time, that the event may not terrify you, as if it had been strange and unexpected.” Besides, he is commanded openly to reprove their blind obstinacy, as if he purposely taunted them.

“My labors will do no good; but it matters not to me: it is enough that what I do obtains the approbation of God, to whom my preaching will be a sweet smell, though it bring death to you.”
(2 Corinthians 2:15.)