Agnipurana 381.29

381.29

dṛśyate tvagryayā budhyā sūkṣmayā sūkṣmadarśibhiḥ /
yacchedvāṅmanasī prājñaḥ tadyacchejjñānamātmani //

But it is seen by subtle intellect, / sharp, by those who perceive what is subtle. / A wise man should restrain speech in the mind; he should restrain that in knowledge, in the self;