Bhagavad Gita 17.24तस्मादोमित्युदाहृत्य यज्ञदानतपःक्रियाः।प्रवर्तन्ते विधानोक्ताः सततं ब्रह्मवादिनाम् ॥

Those who are knowers of the scriptures have a vivid impression of Om in their minds by means of meditation and then they will utter the Pranava with the proper attitude and feeling. Then meditating on Om and uttering it, they perform the sacrifices. Just as a hillstick is very useful in climbing a hill, just as a boat is very useful in crossing a river, so also Om is very useful and important at the commencement of an action or sacrifice.It is not desirable to renounce actions or sacrifices to attain union with the Lord. What is wanted is total and perfect surrender of all actions to God. Sacrifice, charity and austerity are not hindrances to the attainment of Selfrealisation on the contrary the attainment of liberation is rendered easy by their performance without any selfish desires or egoism.