Patanjali Yoga Sutra 1.14

Sanskrit Sutra

स तु दीर्घकालनैरन्तर्यसत्कारासेवितो दृढभूमिः॥१४॥

Swami Vivekananda's translation

It becomes firmly grounded by long constant efforts with great love (for the end to be attained).

Chapter link: Yoga Sutra Chapter 1