KAṬHA UPANISHAD · 2.3.18

मृत्युप्रोक्तां नचिकेतोऽथ लब्ध्वा
विद्यामेतां योगविधिं च कृत्स्नम् ।
ब्रह्मप्राप्तो विरजोऽभूद्विमृत्युरन्योऽप्येवं यो विदध्यात्ममेव ॥ १८॥

mṛtyuproktāṃ naciketo’tha labdhvā
vidyāmetāṃ yogavidhiṃ ca kṛtsnam ।
brahmaprāpto virajo’bhūdvimṛtyuranyo’pyevaṃ yo vidadhyātmameva ॥ 18॥

Thus did Nachiketas with Death for his teacher win the God-knowledge; he learned likewise the whole ordinance of the Yoga: thereafter he obtained Brahman and became void of stain and void of death. So shall another be who cometh likewise to the science of the Spirit.

Sri Aurobindo · CWSA 18, p. 127