Acharya Adishankara on Sahasranama Bhashya
जपस्तु सर्वधर्मेभ्यः परमो धर्म उच्यते ।
अहिम्सया च भूतानां जपयञः प्रवर्तते ॥
In the Mahabharata it is stated; "Of all religious practices, japa (repetition of divine name) is said to be the supreme practice in as much as it is accomplished without animal sacrifice"
Lord Krishna says in Bhagavat Gita
Of all forms of sacrifice, I am the sacrifice of Japa.
एष मे सर्वधर्माणाम् धर्मो अधिकतमो मतः।
यद्भक्त्या पुण्डरीकाक्शं स्तवैरर्चेन्नरः सदा ॥
Taking all these facts into consideration, the great Bhishma said, "Of all the religious practices, I hold this practice (repetition of divine name) to be the best."