KAṬHA UPANISHAD · 2.3.10

यदा पञ्चावतिष्ठन्ते ज्ञानानि मनसा सह ।
बुद्धिश्च न विचेष्टते तामाहुः परमां गतिम् ॥ १०॥

yadā pañcāvatiṣṭhante jñānāni manasā saha ।
buddhiśca na viceṣṭate tāmāhuḥ paramāṃ gatim ॥ 10॥

When the five senses cease and are at rest and the mind resteth with them and the Thought ceaseth from its workings, that is the highest state, say thinkers.