Unperishable

पशुपतित्वज्ञानयोगो नाम पंचमोऽध्यायः 

Pashupati lordship knowledge Chapter 5

उपमन्युरुवाच |

Upamanyu said (to Lord Krishna)

क्षरस्सर्वाणि भूतानि कूटस्थोऽक्षर उच्यते | 11

All living beings (are) perishable/temporary, (while) the unchanging (supreme soul) is called eternal/permanent.

The same half-shloka appears in Bhagavad Gita in Chapter 15, shloka 16.

Shiva and Shakti

गौरीशंकरविभूतियोगो नाम चतुर्थोऽध्यायः

Goddess Parvati and Lord Shiva greatness Chapter 4

उपमन्युरुवाच |

Upamanyu said (to Lord Krishna)

यथा न जायते पुत्रः पितरं मातरं विना |

तथा भवं भवानीं च विना नैतच्चराचरम् | 37

Just as a son is not born without a father (and) a mother, there (would be) no living and non-living beings (world) without Lord Shiva and the supreme Goddess Uma.

Shakti

गौरीशंकरविभूतियोगो नाम चतुर्थोऽध्यायः 

Goddess Parvati and Lord Shiva greatness Chapter 4

उपमन्युरुवाच |

Upamanyu said (to Lord Krishna)

तस्माच्छक्तिमयं सर्वं जगत्स्थावरजंगमम् | 29

Therefore the whole universe, living and non-living beings, is of the form of energy.

Shiva and Shakti

गौरीशंकरविभूतियोगो नाम चतुर्थोऽध्यायः
Goddess Parvati and Lord Shiva greatness Chapter 4



उपमन्युरुवाच |
Upamanyu said (to Lord Krishna)



एवं परस्परापेक्षा शक्तिशक्तिमतोः स्थिता |
न शिवेन विना शक्तिर्न शक्त्या च विना शिवः || 12 ||
In this way (just as sunlight and sun) Goddess Shakti and Shaktiman (Lord Shiva) exist depending on each other. No Lord Shiva without Goddess Shakti and no Goddess Shakti without Lord Shiva.

Pashupati

वायवीयसंहितायामुत्तरभागे कृष्णपुत्रप्राप्तिवर्णनं नाम द्वितीयोऽध्यायः
Vayaviya Samhita, Later/north part, Lord Krishna's son obtaining description Chapter 2



उपमन्युरुवाच |
Upamanyu said (to Lord Krishna)



ब्रह्माद्याः स्थावरांताश्च देवदेवस्य शूलिनः |
पशवः परिकीर्त्यंते संसारवशवर्तिनः || 11 ||
तेषां पतित्वाद्देवेशः शिवः पशुपतिः स्मृतः |
मलमायादिभिः पाशैः स बध्नाति पशून्पतिः || 12 ||
स एव मोचकस्तेषां भक्त्या सम्यगुपासितः | 13
From Lord Brahma to stationary things, under the control of the material world (or Maya), are called the "pashus" of Lord Shiva, the God of the Devas.
Because of his lordship over them, Lord Shiva is considered to be the "Pashupati". The Lord ties/binds the "pashus" with the cord of Maya (the illusion causing power), dirt, etc.
He only is their liberator, (if) worshipped properly by devotion.

Upamanyu's penance

उपमन्युतपोवर्णनं नाम चतुस्त्रिंशोऽध्यायः
Upamanyu's penance description Chapter 34



वायुरुवाच |
Vayudeva said (to the sages)



भक्त्या पञ्चाक्षरेणैव पत्रैः पुष्पैर्वनोद्भवैः |
समभ्यर्च्य चिरं कालं चचार परमं तपः || 54 ||
Worshipping (a Shivalinga made of clay/mud) with leaves and flowers which grow in the forest with the five-lettered (mantra) with devotion for a long time, (Upamanyu) practised penance of the highest level (consuming only wind, not food).

Namah Shivaya

उपमन्युतपोवर्णनं नाम चतुस्त्रिंशोऽध्यायः
Upamanyu's penance description Chapter 34



मातोवाच |
(Upamanyu's) mother said (to Upamanyu)



तस्मान्मन्त्रान्तरांस्त्यक्त्वा पंचाक्षरपरो भव |
तस्मिञ्जिह्वांतरगते न किंचिदिह दुर्लभम् || 46 ||
Therefore (since this mantra is powerful and can protect you always) forget other mantras and become engrossed in the five-lettered (Namah Shivaya). Once it gets on your tongue nothing is difficult to get in this world.



Chapter 32 of Shatarudra Samhita contains the same story and has some similar shlokas.



मंत्रं च ते मया दत्तं गृहाण मदनुज्ञया |
अनेनैवाशु जप्तेन रक्षा तव भविष्यति || 49 ||
And take the mantra given by me by my authorisation. By chanting only this (mantra) quickly your protection will take place.