This material world is impermanent, the demigods are impermanent, and the benedictions derived from the demigods are also impermanent, whereas the living entity is eternal (nityo nityanam cetanas cetananam) - Katha Upanisad 2.2.13

Expressions researched:
"This material world is impermanent, the demigods are impermanent, and the benedictions derived from the demigods are also impermanent, whereas the living entity is eternal (nityo nityānāṁ cetanaś cetanānām (Kaṭha Upaniṣad 2.2.13))"

SB Canto 10.1 to 10.13

"Men of small intelligence worship the demigods, and their fruits are limited and temporary." Worship of demigods may be useful for a limited time, but the result is antavat, perishable. This material world is impermanent, the demigods are impermanent, and the benedictions derived from the demigods are also impermanent, whereas the living entity is eternal (nityo nityānāṁ cetanaś cetanānām (Kaṭha Upaniṣad 2.2.13)).

SB 10.2.26, Translation and Purport:

The demigods prayed: O Lord, You never deviate from Your vow, which is always perfect because whatever You decide is perfectly correct and cannot be stopped by anyone. Being present in the three phases of cosmic manifestation-creation, maintenance and annihilation—You are the Supreme Truth. Indeed, unless one is completely truthful, one cannot achieve Your favor, which therefore cannot be achieved by hypocrites. You are the active principle, the real truth, in all the ingredients of creation, and therefore you are known as antaryāmī, the inner force. You are equal to everyone, and Your instructions apply for everyone, for all time. You are the beginning of all truth. Therefore, offering our obeisances, we surrender unto You. Kindly give us protection.

The demigods or devotees know perfectly well that the Supreme Personality of Godhead is the true substance, whether within this material world or in the spiritual world. Śrīmad-Bhāgavatam begins, therefore, with the words oṁ namo bhagavate vāsudevāya. .. satyaṁ paraṁ dhīmahi (SB 1.1.1). Vāsudeva, Kṛṣṇa, is the paraṁ satyam, the Supreme Truth. The Supreme Truth can be approached or understood by the supreme method, as declared by the Supreme Truth: bhaktyā mām abhijānāti yāvān yaś cāsmi tattvataḥ (BG 18.55). Bhakti, devotional service, is the only way to understand the Absolute Truth. For protection, therefore, the demigods surrender to the Supreme Truth, not to the relative truth. There are persons who worship various demigods, but the Supreme Truth, Kṛṣṇa, declares in Bhagavad-gītā (7.23), antavat tu phalaṁ teṣāṁ tad bhavaty alpa-medhasām: "Men of small intelligence worship the demigods, and their fruits are limited and temporary." Worship of demigods may be useful for a limited time, but the result is antavat, perishable. This material world is impermanent, the demigods are impermanent, and the benedictions derived from the demigods are also impermanent, whereas the living entity is eternal (nityo nityānāṁ cetanaś cetanānām (Kaṭha Upaniṣad 2.2.13)). Every living entity, therefore, must search for eternal happiness, not temporary happiness. The words satyaṁ paraṁ dhīmahi (SB 1.1.1) indicate that one should search for the Absolute Truth, not the relative truth.

While offering prayers to the Supreme Personality of Godhead, Nṛsiṁha-deva, Prahlāda Mahārāja said:

bālasya neha śaraṇaṁ pitarau nṛsiṁha

nārtasya cāgadam udanvati majjato nauḥ

Generally it is understood that the protectors for a child are his parents, but this is not actually the fact. The real protector is the Supreme Personality of Godhead.

taptasya tat-pratividhir ya ihāñjaseṣṭas

tāvad vibho tanu-bhṛtāṁ tvad-upekṣitānām

(SB 7.9.19)

If neglected by the Supreme Personality of Godhead, a child, despite the presence of his parents, will suffer, and a diseased person, despite all medical help, will die. In this material world, where there is a struggle for existence, men have invented many means for protection, but these are useless if the Supreme Personality of Godhead rejects them. Therefore the demigods purposefully say, satyātmakaṁ tvāṁ śaraṇaṁ prapannāḥ: "Real protection can be obtained from You, O Lord, and therefore we surrender unto You,"