There are twelve rasas. Yena tena prakāreṇa manaḥ kṛṣṇe niveśayet (Brs 1.2.4). That is the direction given by Śrīla Rūpa Gosvāmī. "Some way or other, fix up your mind in Kṛṣṇa." Then your life is successful. Some way or other. Yena tena. So if your mind is fixed up always in Kṛṣṇa, then your senses will be also engaged in Kṛṣṇa's service. Because mind is the center of all activities of the senses.
So as Ambarīṣa Mahārāja, he first of all engaged his mind in Kṛṣṇa. Sa vai manaḥ kṛṣṇa-padāravindayoḥ (SB 9.4.18). By fixing up his mind in Kṛṣṇa, then he could use all other senses, namely the tongue . . . actually bhakti begins with the tongue. Sevonmukhe hi jihvādau. Beginning from tongue, kṛṣṇa-bhakti begins. It may be very awkward to hear, that "By tongue, how bhakti begins?" But that is the statement in the śāstra. Ataḥ śrī-kṛṣṇa-nāmādi na bhaved grāhyam indriyaiḥ (CC Madhya 17.136).
Our present senses, blunt, materially covered, it cannot taste what is Kṛṣṇa's name, what is Kṛṣṇa's form, what is Kṛṣṇa's quality, what is Kṛṣṇa's pastime, what is Kṛṣṇa's paraphernalia. Senses, they taste. But . . . just like in . . . when one is suffering from liver disease, or jaundice, he cannot taste the sugar candy. The sugar candy is sweet, but a jaundiced patient, if he's given sugar candy, he'll taste it is bitter.
Similarly, our senses being covered with material consciousness, we cannot at the present moment taste what is Kṛṣṇa's form, what is Kṛṣṇa's name, what is Kṛṣṇa's quality, what is Kṛṣṇa's pastime, what is Kṛṣṇa's paraphernalia, so many things. It is not possible. Ataḥ śrī-kṛṣṇa-nāmādi na bhaved grāhyam indriyaiḥ (CC Madhya 17.136). Our senses are materially contaminated. Therefore we cannot directly perceive, by using our present senses, what is Kṛṣṇa. So it has to be purified.