Is it obligatory to repeat a prayer—whether a fard or a nafl—due to excessive daydreaming and the worshiper's unawareness of what was recited therein?

The worshiper must bring his mind and heart to ponder and achieve humility (khushu') in prayer, and avoid self-talk and fantasies that lead to whisperings (waswasah). Whoever completes their prayer in terms of conditions and pillars, and nothing is lacking except humility, does not have to repeat it. However, their reward is diminished, for in the hadith: "Indeed, a man may depart, and nothing of his prayer is recorded for him except a tenth of it, a ninth of it, an eighth of it, a seventh of it, a sixth of it, a fifth of it, a fourth of it, a third of it, or half of it."