Yoga Sutras of Patanjali · 1.14

स तु दीर्घकालनैरन्तर्यसत्कारासेवितो दृढभूमिः ॥१४॥

sa tu dīrghakālanairantaryasatkārāsevito dṛḍhabhūmiḥ

Practice becomes firmly grounded when it is continued for a long time, without interruption, and with devotion.

— Yoga Sutras of Patanjali 1.14

Source: Sanskrit attributed to Patanjali (c. 2nd century BCE – 4th century CE). Public-domain English readings drawn from Swami Vivekananda's 'Raja Yoga' (1896) and Charles Johnston's 'The Yoga Sutras of Patanjali' (1912).