Mahabharata 12.330.16

निर्वाणं परमं सौख्यं धर्मोऽसौ पर उच्यतेतस्मान्न च्युतपूर्वोऽहमच्युतस्तेन कर्मणा

nirvāṇaṃ paramaṃ saukhyaṃ dharmo'sau para ucyatetasmānna cyutapūrvo'hamacyutastena karmaṇā

Our plain-language meaning of this verse is waiting for scholar review.