Verse 3.13.2

अथ योऽस्य दक्षिणः सुषिः स व्यानस्तच्छ्रोत्रं स चन्द्रमास्तदेतच्छ्रीश्च यशश्चेत्युपासीत श्रीमान्यशस्वी भवति य एवं वेद ॥ ३.१३.२ ॥

atha yo'sya dakṣiṇaḥ suṣiḥ sa vyānastacchrotraṃ sa candramāstadetacchrīśca yaśaścetyupāsīta śrīmānyaśasvī bhavati ya evaṃ veda || 3.13.2 ||

2. Next, the southern door of the heart is vyāna. It is also the ears, and it is the moon. Worship it as the source of prosperity and fame. He who knows this becomes prosperous and famous.

Word-for-word explanation:

Atha, next; yaḥ asya dakṣiṇaḥ suṣiḥ, that which is its southern passage; saḥ vyānaḥ, that is vyāna; tat śrotram, that is [also] the ear; saḥ candramāḥ, [and] that is the moon; tat etat, it is that; śrīḥ ca yaśaḥ iti upāsīta, meditate on as prosperity and fame; yaḥ evam veda, he who knows this; śrīmān yaśasvī bhavati, becomes fortunate and famous.

Commentary:

Vyāna is the air that is spread all over the body. It is also the breath you need when you are doing some hard work. Vyāna is the door, or passage, in the southern part of the heart, and it is connected with hearing and the moon.

A person learns by hearing, so the ear is said to be the source of knowledge. The moon is the source of food, which gives a person strength, and from strength and knowledge a person acquires prosperity and fame. By worshipping vyāna as Brahman a person can attain heaven, which is his primary concern, and secondarily he attains prosperity and fame.