śraddhātrayavibhāgayoga - Verse śloka 16
śloka 16
manaḥ prasādaḥ saumyatvaṃ maunamātmavinigrahaḥ |
bhāvasaṃśuddhirityetattapo mānasamucyate ||17-16||
Translation
Cheerfulness of mind, gentleness, silence, self-restraint and purity of the inner being—all this is called austerity of the mind.