Manava Dharmashastra 1.93

1.93

‘uttamāṅga’, mūrdhā tata udbhava utpattirbrāhmaṇasya | jyeṣṭhaścāsāvanyebhyo varṇebhyaḥ pūrvaṃ brahmaṇā sṛṣṭaḥ | ‘brahmaṇo’ vedasya dhāraṇāttasya hi saviśeṣaṃ tadvihitamataḥ sarvasva jagato'smāddhetutrayād brāhmaṇaḥ prabhuḥ prabhuriva | prabhurvinayenopasarpaṇīyaḥ, tadājñāyāṃ ca dharme sthātavyam | dharmataḥ prabhurdharme prabhurityarthaḥ | ādyāditvāttasiḥ |

In matters regauding ‘Dharma’, the Brāhmaṇa is the Lord of this whole world;—because he sprang out of the best part of (Prajāpati’s) body, because he is the eldest ok all, and because he upholds the Veda.—(98)

Medhātithi’s commentary (manubhāṣya):
This verse explains what follows from what has been said in the preceding verse. ‘The best part of the body,’—the head; from out of that sprang, was born, the Brāhmaṇa.—He is also ‘the eldest of all,’—the Brāhmaṇa was produced before the other castes .— ‘Because he upholds the Brahman, i.e., Veda’; the upholding of the Veda has been specifically prescribed for him.—‘Hence,’—for all these three reasons,—‘the Brāhmaṇa is the lord,’—i.e., as if he were the lord —‘of this whole world’; i.e., he should be approached (treated) like the lord; and people should obey his orders in matters relating to Dharma.—‘Dharmataḥ prabhuḥ’ means ‘dharme prabhuḥ,’—‘Lord in matters regarding Dharma,’—the affix ‘tasi’ (in ‘dharmataḥ’) being added according to the Vārtika on Pāṇini 5.4.44, which lays down the use of this affix in connection with such terms as ‘ādya’ and the like. (93)