This statement “Uttishthata Jagrata Prapya Varan Nibodhata” ( उत्तिष्ठत जाग्रत प्राप्य वरान्निबोधत ) is part of dialogues between Yama and Nachiketa, and is mentioned in Katho Upanishad 1.3.14
Nachiketa was sent to Yama, the Hindu god of death, by his father Vajashrava.
He asks Yama to taught him Self-knowledge ( Brahma Gyana), in this shloka Yama is advising Nachiketa to rise, awake and not stop until he learns this self knowledge from the learned teachers.
उत्तिष्ठत जाग्रत प्राप्य वरान्निबोधत।
क्षुरस्य धारा निशिता दुरत्यया दुर्गं पथस्तत्कवयो वदन्ति ॥
Arise, awake, find out the great ones and learn of them; for sharp as a knife’s edge, hard to traverse, difficult of going is that path, say the sages.
”उठो, जागो, वरिष्ठ पुरुषों को पाकर उनसे बोध प्राप्त करो। छुरी की तीक्ष्णा धार पर चलकर उसे पार करने के समान दुर्गम है यह पथ-ऐसा ऋषिगण कहते हैं।