Is expressing exasperation or distress inwardly – and not vocally – at a parent's request considered an act of disobedience or a major sin?

Feeling burdened by parental commands is not disobedience unless annoyance and exasperation are shown to the parents. What is forbidden is confronting them with such feelings, as Allah Almighty says: "So do not say to them [anything that indicates] displeasure" (Quran 17:23); meaning, do not let them hear any bad word, not even the slightest of bad words. The child should strive to control himself so as not to utter anything that indicates annoyance or weariness, and accustom himself to meet their commands with satisfaction and cheerfulness, and bring to mind the good intention and the great reward for honoring one's parents.