The Law Code of Yājñavalkya 3.1.72

3.1.72

iti sparśāśrupātayor upavāsa uktaḥ | asau kṛcchreṣv aśaktasya tathā bandhanacchedane dahane vā māsaṃ bhaikṣāhāras triṣavaṇaṃ ca iti sumantunā bhaikṣāśitvam uktaṃ tad apy aśaktasyaiva | evam anyāny api tadviṣayāṇi smṛtivākyāni vyavasthāpanīyāni | ayaṃ ca dāhādipratiṣedho nityakarmānuṣṭhānāsamarthajīrṇavānaprasthādivyatiriktaviṣayaḥ, teṣām abhyanujñādarśanāt,

—this fast stated for touching or shedding tears applies to one unable to perform the kṛcchras. Likewise, Sumantu stated, "eating alms for a month and three daily ablutions for cutting the bonds or burning"—eating alms also applies solely to one unable. In this manner other smṛti texts on this subject are also to be reconciled. Furthermore, this prohibition against burning and the like applies to cases other than decrepit forest ascetics and the like who are incapable of performing regular duties, because permission for them is observed: