Srimad-Bhagavatam: Canto 4 - Chapter 1 - Verse 49

Sanskrit:

मुख्या नाम पुरस्ताद् द्वास्तयापणबहूदनौ ।विषयौ याति पुरराड्रसज्ञविपणान्वित: ॥ ४९ ॥

ITRANS:

mukhyā nāma purastād dvāstayāpaṇa-bahūdanauviṣayau yāti pura-rāḍrasajña-vipaṇānvitaḥ

Translation:

The fifth gate situated on the eastern side was named Mukhyā, or the chief. Through this gate, accompanied by his friends named Rasajña and Vipaṇa, he used to visit two places named Bahūdana and Āpaṇa.

Purport:

The mouth is here described as the chief or the most important gate. The mouth is a very important entrance because one has two functions to conduct with the mouth. One function is eating, and the other is speaking. Our eating is done with the friend Rasajña, the tongue, which can taste so many different types of foods. The tongue is also used for speaking, and it can speak of either material sense enjoyment or Vedic knowledge. Of course, here material sense enjoyment is stressed. Therefore the word rasajña is used.