Patanjali Yoga Sutra 2.1

Sanskrit Sutra

तपः-स्वाध्यायेश्वरप्रणिधानानि क्रियायोगः॥१॥

Swami Vivekananda's translation

Mortification, study, and surrendering fruits of work to God are called Kriyā-Yoga.

Chapter link: Yoga Sutra Chapter 2