One verse

Bhagavad Gita 17.24

17.24

तस्मादोमित्युदाहृत्य यज्ञदानतपःक्रियाः | प्रवर्तन्ते विधानोक्ताः सततं ब्रह्मवादिनाम् ||१७-२४||

tasmādomityudāhṛtya yajñadānatapaḥkriyāḥ . pravartante vidhānoktāḥ satataṃ brahmavādinām ||17-24||

tasmāt
therefore
oṁ
beginning with oṁ
iti
thus
udāhṛtya
indicating
yajña
of sacrifice
dāna
charity
tapaḥ
and penance
kriyāḥ
performances
pravartante
begin
vidhāna-uktāḥ
according to scriptural regulation
satatam
always
brahma-vādinām
of the transcendentalists
tat
that
iti
thus

Therefore, transcendentalists undertaking performances of sacrifice, charity and penance in accordance with scriptural regulations begin always with oṁ, to attain the Supreme.