But I, as a deaf man, hear not, etc. The inspired writer here compares himself to a dumb and deaf man, for two reasons. In the first place, he intimates that he was so overwhelmed with the false and wicked judgments of his enemies, that he was not even permitted to open his mouth in his own defense. In the second place, he alleges before God his own patience, as a plea to induce God the more readily to have pity upon him; for such meekness and gentleness, not only with good reason, secures favor to the afflicted and the innocent, but it is also a sign of true piety. Those who depend upon the world, and have respect only to men, if they cannot avenge the injuries that are done them, plainly show by their loud complaints the burning rage and fury of their hearts. In order, therefore, that a man may quietly and patiently endure the insolence, violence, calumny, and deceit of his enemies, it is necessary that he trust in God. The man who is fully persuaded in his own heart that God is his defender, will cherish his hope in silence, and, calling upon him for help, will lay a restraint upon his own passions. Accordingly, Paul, in Romans 12:19, very properly says, that we "give place unto wrath" when, oppressed before the world, we nevertheless still repose on God. On the other hand, whoever gives loose reins to his passions, takes away as much as he can from God, to whom alone it belongs, the right of taking vengeance, and deprives himself of his assistance. It is indeed certain, that if David had obtained a hearing, he would have been ready to defend his own innocence; but perceiving that it availed him nothing, nay, that he was shut out and debarred from all defense of his cause, he humbly submitted, waiting patiently for the heavenly Judge. He therefore says that he held his peace, as if he had already been convicted and struck dumb. And it is indeed very difficult, when we are conscious of our own innocence, patiently and silently to bear an unjust condemnation, as if all argument had failed us, and we had no excuse or reply left us.

But I, as a deaf man, heard not - I was as if I had been deaf, and did not hear them or know what they were about. I took no notice of what they did anymore than if I had not heard them. That is, he did not reply to them; he did not become angry; he was as calm and patient as if they had said nothing.
And I was as a dumb man that openeth not his mouth - As if I were a man that could not speak. I was perfectly silent under all this persecution. Compare 2-Samuel 16:10. How eminently true was this of the Saviour! Isaiah 53:7; 1-Peter 2:23; Matthew 26:63; Matthew 27:12, Matthew 27:14.

But I, as a deaf man - I was conscious of my guilt, I could not vindicate myself; and I was obliged in silence to bear their insults.

But I, as a (k) deaf [man], heard not; and [I was] as a dumb man [that] openeth not his mouth.
(k) For I can have no audience before men, and therefore patiently wait for the help of God.

But I, as a deaf man, heard not,.... He acted the part of a deaf man, and made as if he did not hear the mischievous things his enemies spoke; as Saul, when the sons of Belial spoke against him and despised him, 1-Samuel 10:27; and as our Lord when his enemies accused him, Matthew 27:12;
and I was as a dumb man, that openeth not his mouth; made no reply to what they said, and did not render railing for railing; in which Christ was the antitype of him, Isaiah 53:7.

He patiently submits, uttering no reproaches or replies (John 19:9) to their insulting speeches;

Dumb - Was silent, to testify his humiliation for his sins, and his acceptation of the punishment which he had brought upon himself.