Bhagavad Gita 17.16 — Austerity of mind

मनः प्रसादः सौम्यत्वं मौनमात्मविनिग्रहः। भावसंशुद्धिरित्येतत्तपो मानसमुच्यते ॥

manaḥ prasādaḥ saumyatvaṃ maunamātmavinigrahaḥ | bhāvasaṃśuddhirityetattapo mānasamucyate ||

Meaning

Contentment of mind, gentleness, silence, self-control and purity of feeling — this is called austerity of the mind.