सत्येन लभ्यस्तपसा ह्येष आत्मा सम्यग्ज्ञानेन ब्रह्मचर्येण नित्यम्

Through continuous pursuit of Satya (truthfulness), Tapas (perseverance, austerity), Samyajñāna (correct knowledge), and Brahmacharya, one attains Atman (Self, Soul).

— Mundaka Upanishad, 3.1.5