SB 1.19.6
ya vai lasac-chri-tulasi-vimisra-
krsnanghri-renv-abhyadhikambu-netri
punati lokan ubhayatra sesan
kas tam na seveta marisyamanah
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The river [by which the King sat to fast] carries the most auspicious water, which is mixed with the dust of the lotus feet of the Lord and tulasi leaves. Therefore that water sanctifies the three worlds inside and outside and even sanctifies Lord Siva and other demigods. Consequently everyone who is destined to die must take shelter of this river.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Maharaja Pariksit, just after receiving the news of his death within seven days, at once retired from family life and shifted himself to the sacred bank of the Yamuna River. Generally it is said that the King took shelter on the bank of the Ganges, but according to Srila Jiva Gosvami, the King took shelter on the bank of the Yamuna. Srila Jiva Gosvami’s statement appears to be more accurate because of the geographical situation. Maharaja Pariksit resided in his capital Hastinapura, situated near present Delhi, and the river Yamuna flows down past the city. Naturally the King would take shelter of the river Yamuna because she was flowing past his palace door. And as far as sanctity is concerned, the river Yamuna is more directly connected with Lord Krsna than the Ganges. The Lord sanctified the river Yamuna from the beginning of His transcendental pastimes in the world. While His father Vasudeva was crossing the Yamuna with the baby Lord Krsna for a safe place at Gokula on the other bank of the river from Mathura, the Lord fell down in the river, and by the dust of His lotus feet the river at once became sanctified. It is especially mentioned herein that Maharaja Pariksit took shelter of that particular river which is beautifully flowing, carrying the dust of the lotus feet of Lord Krsna, mixed with tulasi leaves. Lord Krsna’s lotus feet are always besmeared with the tulasi leaves, and thus as soon as His lotus feet contact the water of the Ganges and the Yamuna, the rivers become at once sanctified. The Lord, however, contacted the river Yamuna more than the Ganges. According to the Varaha Purana, as quoted by Srila Jiva Gosvami, there is no difference between the water of the Ganges and the Yamuna, but when the water of the Ganges is sanctified one hundred times, it is called the Yamuna. Similarly, it is said in the scriptures that one thousand names of Visnu are equal to one name of Rama, and three names of Lord Rama are equal to one name of Krsna.