Thomas Aquinas Commentary Lamentations 3:28-30

"Let him sit alone and keep silence, because he hath laid it upon him. Let him put his mouth in the dust, if so be there may be hope. Let him give his cheek to him that smiteth him; let him be filled full with reproach." — Lamentations 3:28-30 (ASV)

Here the author describes the condition of the one who waits.

1. Regarding the depth of his contemplation: he is solitary, so as not to be disturbed; he will be silent, away from the turmoil of thoughts and desires, because by this, he has raised himself above himself to contemplate divine things. I will lead her into the wilderness, and I will speak to her heart (Hosea 2:14). Alternatively, this shows the humiliation of the one who waits, because he remains in expectation: he will sit solitary and be silent because he is humiliated, and he will raise himself up in pride.
2. Regarding the humility of his speech: he will put his mouth in the dust by speaking humbly. Your speech shall be heard out of the ground (Isaiah 29:4).
3. Regarding his endurance of tribulation: he will give his cheek to the one who strikes him, or at least be ready to give it. If someone strikes you on your right cheek, turn to him the other also (Matthew 5:39). He will be filled with it; he will delight in it, so to speak, hoping for this favor. Not only so, but we glory in tribulations also (Romans 5:3). I have given my body to the strikers, and my cheeks to those who plucked them (Isaiah 50:6).