Bhagavad-gītā 17.24
BG 17.24
Open the full passageतस्मादोमित्युदाहृत्य यज्ञदानतपःक्रियाः । प्रवर्तन्ते विधानोक्ताः सततं ब्रह्मवादिनाम् ॥२४॥
Sanskrit
tasmād oṁ ity udāhṛtya yajña-dāna-tapaḥ-kriyāḥ pravartante vidhānoktāḥ satataṁ brahma-vādinām
Translation
Therefore, transcendentalists undertaking performances of sacrifice, charity and penance in accordance with scriptural regulations begin always with oṁ, to attain the Supreme.