Anguttara Nikaya 1:13
SUJATOIdaṁ kho, bhikkhave, atthavasaṁ paṭicca ‘jarādhammomhi, jaraṁ anatīto’ti abhiṇhaṁ paccavekkhitabbaṁ itthiyā vā purisena vā gahaṭṭhena vā pabbajitena vā.
This is the advantage for a woman or a man, a layperson or a renunciate of often reviewing this: ‘I am liable to grow old, I am not exempt from old age’.