Manava Dharmashastra 5.126

5.126

bhūmigrahaṇamupalakṣaṇārtham | tena praṇālīkāgatā api śucaya eva | svabhāvaśucayo hyāpo bhūmigatā ākāśagatāśca | kintu bhūmeramedhyadravyasaṃsargātkiṃcidaśucitvam | tatra gatānāṃ sargato'śucitvaprāptau yāvatīnāṃ ca śuddhirastadarthamidaṃ vaitṛṣṇyaṃ yāsu gorbhavediti | vaitṛṣṇyaṃ pipāsāvicchedaḥ | parimāṇopalakṣaṇārthaṃ caitat | tatra cirantanairvyākhyātaṃ liṅgadarśanena “yathā vai goḥ sāsnāmbhasi plāvyeti” | yatra goḥ sāsnādi majjati tṛṣṇā ca vicchidyate tāvatyaḥ |
yāstu medhyabhūmigatāstāḥ svalpā api śuddhāḥ |
kathaṃ punaramedhyavyāptiravaseyā | gandhavarṇarasānvitāḥ | ‘amedhyeneti’ tṛtīyāntaṃ ṣaṣṭhyā vipariṇamyate | amedhyasambandhibhirgandhādibhiryadyanvitāḥ saṃyuktā bhavanti, tato vyāptā ucyante | evaṃ ca kṛtvā pānīyaṃ taḍāgādiṣu yadyekasminpradeśe'medhyaṃ dṛśyate, pradeśāntare gandhādiśūnyaṃ śuddhameveva |

Medhātithi’s commentary (manubhāṣya):
The ‘ground’ is mentioned only by way of illustration; so that water in canals is also pure. Water on the ground, as also in the atmosphere, is, by its very nature, pure; but the ground, being in contact with unclean substances, is slightly impure; hence when water is collected on the ground, it imbibes impurity by contact; and the present text proceeds to point out what quantity of water thus collected is to be regarded as pure:—‘Sufficient to allay the thirst of the cow’;—‘vaitṛṣṇyam’ means freedom from thirst, This is meant to indicate a particular quantity; this explanation having been adopted by the ancients on the strength of the words of the Veda—‘so that the dawlap of the cow dapples in water &c. &c.’ Thus the quantity meant is that in which the cow’s dewlap becomes submerged, or which allays her thirst.

Water collected on pure ground is pure, even in small quantities.

“How is it to be known that water has been ‘contaminated by an unclean thing’?”

In answer to this we have the phrase—‘becoming affected by its smell, colour and taste,’ The Instrumental ending in ‘amedhyena’, ‘by an unclean thing’, has to be changed here into the genitive; the meaning being—‘when the water imbibes the smell, colour and taste of the unclean thing, then it is to be regarded as contaminated by it.’ According to this construction, if in a tank, an unclean thing be found in one part, while in another part the water be found to be free from its smell &c., then this latter is to be regarded as pure—(126).