Heart radical at the bottom — the full 4-stroke form (rather than the left-side 忄 variant). 恕 means 'forgive / be lenient', a heart-based virtue, so 心 is fully semantic. Joins the heart family with 想 think, 愿 wish, 怒 anger, 忍 endure.
Phonetic — 如 rú → 恕 shù (irregular shift). 如 means 'as / like / according to', a meaning Confucius drew on for 恕: treating others as you would yourself. The Analects defines 恕 as 己所不欲,勿施于人 'don't do to others what you don't want done to yourself' — a literal 'as-heart' ethic.