Bhagavad Gita 18.46
One reaches perfection by dedicating their actions to God, Who is the source of all being and fills everything.
यतः प्रवृत्तिर्भूतानां येन सर्वमिदं ततम्।स्वकर्मणा तमभ्यर्च्य सिद्धिं विन्दति मानवः॥yataḥ pravṛttirbhūtānāṃ yena sarvamidaṃ tatam|svakarmaṇā tamabhyarcya siddhiṃ vindati mānavaḥ||
English translation (above): Shri Purohit Swami (1935), public domain. Sanskrit text via github.com/gita/gita (Unlicense).