Taittirīyopaniṣat 02.16

yadā hyevaiṣa etasminnadṛśye anātmye anirukte anilayane abhayaṃ pratiṣṭhāṃ vindate। atha so'bhayaṃ gato bhavati। yadā hyevaiṣa etasminnudaramantaraṃ kurute। atha tasya bhayaṃ bhavati। tattveva bhayaṃ viduṣo'manvānasya॥

When one finds the foundation of fearlessness in that which is unseen, that 'anātmya', undefined, and without abode, then he attains fearlessness. But when one creates distinction within this (i.e he is independent from this essence), then fear arises for him. That indeed is truly fear for the knower who perceives difference.

tad apy eṣa śloko bhavati। bhīṣāsmād vātaḥ pavate। bhīṣod eti sūryaḥ। bhīṣāsmād agniś cendraś ca। mṛtyur dhāvati pañcama iti ॥16॥

There is also this verse: "From fear of Him the wind blows, from fear the sun rises, from fear of Him fire and Indra, and Death as the fifth, run their courses."

Taittirīya Bhāshya 02.16

The Lord is said to be 'anātma', as He is different from the individual beings in terms of attributes. The supreme Viṣṇu alone is described as 'ā', as is higher than all other principles and beings. He is infinite in qualities, unexpressed and without dependence. An individual being begets fear when he thinks he is independent of Lord Vishnu. Liberated beings, such as the wise Vāyu and others, who governs the universe, are fearless because they always perform their duties directly to please Lord Viṣṇu.

"tasmādadṛśye jaivānāṃ guṇānāmapyasaṅgateḥ। anātmye'tha guṇānantyādanirukte nirāśrayāt॥ anilayane'bhayatvena yadā jñānena tiṣṭhati। tadā'bhayaṃ hariṃ gacchennaivā-jñānī kathaṃcana॥

"Therefore, that which is unseen and not associated even with the limited qualities of living beings is termed as 'anātma', i.e. not the individual being; He is infinite in qualities, unexpressed and without support. One attains Hari (the Supreme) when one is not dependent on any abode, is in a state of fearlessness and remains in knowledge; but the ignorant never attains Him in any way.

yadaitasmin pare viṣṇāvudaraṃ jīvagatvataḥ। bhedaṃ karoti tenaiva bhayamasya mahad bhavet॥

If one creates division in this Supreme Lord Viṣṇu, the origin of all living beings, then from that very act, great fear arises for him.

ā ity uktaḥ paro viṣṇur ebhya ucca sa eva tu। ta udā jīvasaṅghāḥ syur udaraṃ tadgatāntaram॥ tadeva brahma bhayakṛd viduṣo'viduṣas tathā। viduṣo'lpabhayaṃ kuryād yāvan muktiṃ vrajaty asau॥

The supreme Viṣṇu, thus described as 'ā' alone, is higher than all these. From him arise the groups of living beings, who may be within the belly, having entered there. That very Brahman is the source of fear for both the wise and the ignorant. For the wise, it causes only little fear until they attain liberation.

athābhayaṃ bhaved brahma tasya muktasya sarvadā। tasmād vāyvādayo devā vidvāṃso'pi viśeṣataḥ॥

Now, for the liberated one, Brahman is always fearlessness. Especially this is so with the gods beginning with Vāyu, the wise.

bhītāḥ svakarma kurvanti viṣṇoḥ prītyarthamañjasā। amanvānasya nurviṣṇuḥ kuryānnityaṃ mahadbhayam॥ tamākhyamanutthānam .... ॥"

Out of fear, people perform their duties directly to please Lord Viṣṇu. For one who does not follow, the great Viṣṇu would always instil great fear. This is called inaction ...."