The Yoga of Liberation by Renunciation

Krishna explains the first kind of improper relinquishment. 'Niyatasya tu sannyāsaḥ karmaṇo nopapadyate'—renunciation of prescribed duties (niyatasya karmaṇaḥ) is not proper (na upapadyate). Prescribed duties (yajña, dāna, tapaḥ) should not be renounced. Then he explains what happens when someone does abandon them: 'mohāt tasya parityāgaḥ tāmasaḥ parikīrtitaḥ'—abandonment (parityāgaḥ) of duty out of delusion (mohāt) is declared to be tamasic (tāmasaḥ). This is the first kind of improper tyaga: abandoning prescribed duties out of ignorance or delusion. It's tamasic because it comes from misunderstanding—thinking you should renounce duty when you should perform it with detachment. This clarifies the distinction: you don't renounce prescribed duties, you perform them without attachment.