Bhagavad Gita · 2.66

नास्ति बुद्धिरयुक्तस्य न चायुक्तस्य भावना।न चाभावयतः शान्तिरशान्तस्य कुतः सुखम्॥

nāsti buddhir ayuktasya na chāyuktasya bhāvanā na chābhāvayataḥ śhāntir aśhāntasya kutaḥ sukham

For one who is not united with the Self, there is no wisdom, no meditation. For one without meditation, there is no peace. And for one without peace, how can there be happiness?

— Bhagavad Gita 2.66

Source: Sacred-Texts.com (Sanskrit) + Bhagavad-Gita.io (translations)