BG 17.16
मनःप्रसादः सौम्यत्वं मौनमात्मविनिग्रहः
भावसंशुद्धिरित्येतत्तपो मानसमुच्यते
manaḥprasādaḥ saumyatvaṃ maunamātmavinigrahaḥ
bhāvasaṃśuddhirityetattapo mānasamucyate
TRANSLATION
Serenity of mind, benevolence, silence, self-control, purity of mind—these are called austerity of the mind.
PURPORT
Serenity of mind, viz., absence of wrath etc., practice of benevolence, viz., the direction of the mind for the good of others, silence, viz., control of speech by the mind; self-control, viz., focusing the activity of the mind on the object of contemplation; purity of mind, viz., absence of thought about subjects other than the self—these constitute the austerity of the mind.