Bhagavad Gita 6.18

यदा विनियतं चित्तमात्मन्येवावतिष्ठते।
निःस्पृहः सर्वकामेभ्यो युक्त इत्युच्यते तदा।।6.18।।

Yada viniyatam chittamatmanyevavatishthate
Nihsprihah sarvakamebhyo yukta ityuchyate tada

Simple meaning, written by AIWhen the restrained mind rests firmly in the Self alone and is free from longing for all desires, one is then said to be united (yukta).

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