Verse 2.19.2

स य एवमेतद्यज्ञायज्ञीयमङ्गेषु प्रोतं वेदाङ्गी भवति नाङ्गेन विहूर्छति सर्वमायुरेति ज्योग्जीवति महान्प्रजया पशुभिर्भवति महान्कीर्त्या संवत्सरं मज्ज्ञो नाश्नीयात्तद्व्रतं मज्ज्ञो नाश्नीयादिति वा ॥ २.१९.२ ॥
॥ इति एकोनविंशः खण्डः ॥

sa ya evametadyajñāyajñīyamaṅgeṣu protaṃ vedāṅgī bhavati nāṅgena vihūrchati sarvamāyureti jyogjīvati mahānprajayā paśubhirbhavati mahānkīrtyā saṃvatsaraṃ majjño nāśnīyāttadvrataṃ majjño nāśnīyāditi vā || 2.19.2 ||
|| iti ekonaviṃśaḥ khaṇḍaḥ ||

2. He who knows that the Sāma known as Yajñāyajñīya is located in different parts of the body becomes possessed of a firm body and none of his organs has any defect. He has a long and brilliant life; and he becomes great because of his children and his animal wealth. He also becomes famous for his great deeds. His vow is that he will not eat meat for one whole year, or he will not eat it at all.

Word-for-word explanation:

Saḥ yaḥ evam etat yajñāyajñīyam aṅgeṣu protam veda, he who knows that this Sāma called Yajñāyajñīya is located in the different parts of the body; aṅgī bhavati, has a firm body; na aṅgena vihūrchati, has no defect in his limbs or organs; sarvam āyuḥ eti, he lives the full span of his life; jyok jīvati, he has a brilliant life; mahān prajayā paśubhiḥ bhavati, he becomes great in respect of his children and his animal wealth; mahān kīrtyā, he becomes great because of his great deeds; saṃvatsaram, for one whole year; majjñaḥ, meat; na aśnīyāt, will not eat; majjñaḥ na aśnīyāt iti vā, or will not eat meat at all; tat vratam, this is his vow. Iti ekonaviṃśaḥ khaṇḍaḥ, here ends the nineteenth section.

Commentary:

‘A firm body’ means a good, sound body with none of its organs or limbs defective. Even his nails and his hair will be normal.

The word majjña, meat, is in the plural here. This implies that both fish and meat should be avoided.