sa brahmā sa śivaḥ sendraḥ so'kṣaraḥ paramaḥ svarāṭ । sa eva viṣṇuḥ sa prāṇaḥ sa kālo'gniḥ

sa candramāḥ (8) Kaivalya Upanishad

Meaning: He is Brahma, He is Siva, He is Indra, He is the liberated Jiva (akshara), He is the

celebrated Master of Karma. He alone is Vishnu, He is the Vital Breath, He is Time, He is
Agni, He is the Moon.

1. यस्मिन्निदं सर्वमोतप्रोतं तस्मादन्यन्न परं किञ्चनास्ति ।न तस्मात्पूर्वं न परं तदस्ति न भूतं

नोत भव्यं यदासीत् । (Atharvasiras Upanishad 5:5)  
2. “There is none greater than Rudra, on whom all the worlds are
strung like beads. Over ages, nothing so far in the past was ever
greater than him and nothing is going to be greater than him in
future”. 
3. यो वै रुद्रः स भगवान्यच्च ते जस्तस्मै वै नमोनमः ॥ (Atharvasiras Upanishad
2:19)  
4. “He who is Rudra, he alone is Supreme god (Bhagawan). He is
the Supreme Light and we salute him again and again 
5. सर्वकरणानि मनसि सम्प्रतिष्ठाप्य ध्यानं विष्णु ः प्राणं मनसि सह करणै ः सम्प्रतिष्ठाप्य
ध्याता रुद्रः प्राणं मनसि सहकरणै र्नादान्ते परमात्मनि सम्प्रतिष्ठाप्य ध्यायीते शानं प्रध्यायितव्यं
सर्वमिदं |(Atharvashika Upanishad 2:1) 
6. “The pranava (the sound of Om) makes all the souls to bow
before it. It is the one and only one which has to be meditated
upon as the four Vedas and the birth place of all devas. One who
meditates like that goes away from all sorrows and fears and gets
the power to protect all others who approach him. It is because of
this meditation only that Lord Vishnu who is spread every where,
wins over all others. It is because Lord Brahma controlled all his
organs and meditated upon it, he attained the position of the
creator. Even Lord Vishnu , parks his mind in the sound (Om) of the
place of Paramathma (ultimate soul) and meditates upon Îsâna. , who
is most proper to be worshipped. All this is only proper in case of
Îsâna. ”. 
7. स एव सर्वं यद्भत ू ं यच्च भव्यं सनातनम् ।ज्ञात्वा तं मृ त्यु मत्ये ति नान्यः पन्था विमु क्तये ॥
(Kaivalya Upanishad 9)  
8. “Meditating on the highest Lord, allied to Uma, powerful,
three-eyed, blue-necked, and tranquil, the holy man reaches Him
(Shiva) who is the source of all, the witness of all and is beyond
darkness (i.e. Avidya). He alone is all that was, and all that will
be, the Eternal; knowing Him, one transcends death; there is no
other way to freedom”. 
9. एतज्ज्ञे यं नित्यमे वात्मसं स्थं नातः परं वे दितव्यं हि किञ्चित् ।  
10. भोक्ता भोग्यं प्रेरितारं च मत्वासर्वं प्रोक्तं त्रिविधं ब्रह्ममे तत् ॥(Svetasvatara
Upanishad 1:12) 
11. “The enjoyer (jiva), the objects of enjoyment and the Ruler
(Isvara)—the triad described by the knowers of Brahman—all this is
nothing but Brahman (Rudra). This Brahman (Rudra) alone, which
abides eternally within the self, should be known. Beyond it,
truly, there is nothing else to be known 
12. सोऽहं सर्वाकारः । यतो वा इमानि भूतानि जायन्ते ।ये न जातानि जीवन्ति ।
यत्प्रयन्त्यभिसं विशन्ति । तं मामे वविदित्वोपासीत । भूतेभिर्दे वे भिरभिष्टु तोऽहमे व । भीषास्माद्वातःपवते
। भीषोदे ति सूर्यः ।भीषास्मादग्निश्चे न्द्रश्च । सोमोऽतएव योऽहं सर्वेषामधिष्ठाता सर्वेषां च
भूतानांपालकः । सोऽहं पृ थिवी । सोऽहमापः । सोऽहं ते जः । सोऽहं वायु ः ।सोऽहं कालः ।
सोऽहं दिशः । सोऽहमात्मा । मयि सर्वं प्रतिष्ठितम् ।ब्रह्मविदाप्नोति परम् । ब्रह्मा शिवो मे
अस्तु सदाशिवोम् ।(Bhasmajabala Upanishad) “I myself am that Great Lord
Siva, God of all gods, and the Supreme Controller of all the
universes. I am that Brahman, I am Omkara; I am the Creator,
Preserver and Destroyer of all. Through My terror only, vayu blows,
through my terror only Surya shines, through my terror only fire
burns, Indra also function properly through my terror. I am this
world and the five elements. I am the Highest Truth that exists,
the Brahman of the Upanishads”. 

Mahabharata says in Kaliyuga only surrender to Lotus feet of Lord Shiva can give moksha

haracaraṇaniratamatinā bhavitavyamanārjavaṃ yugaṃ prāpya ||” (MBH 13:14:183a)

“When the unrighteous or sinful Kali Yuga comes, one should never pass a moment
without devoting his heart upon the feet of Hara(Shiva)”.

Shiva Purana says everyone worship Lord Shiva but Lord Shiva don't know anyone

Shiva Purana, Kotirudra Samhita 7:15)

“Everyone worships Maha Rudra but Maha Rudra doesn’t worship anyone. For the sake
of devotees he meditates on himself”

Lord Vishnu the great Devotee of Shiva as per Vedas.

Shatapatha Brahmana of Shukla Yajur-Veda describes how nArAyan Rishi become one with
Mahadev.

"puruṣo ha nārāyaṇo'kāmayata atitiṣṭheyaṃ sarvāṇi bhūtānyahamevedaṃ sarvaṃ syāmiti sa

etam puruṣamedham pañcarātram yajñakratumapaśyattamāharattenāyajata
teneṣṭvātyatiṣṭhatsarvāṇi bhūtānīdaṃ sarvamabhavadatitiṣṭhati sarvāṇi bhūtānīdaṃ sarvam
bhavati ya evam vidvānpuruṣamedhena yajate yo vaitadevam veda" ( Sathapatha
Brahmana 13:6:1:1)

Meaning:

"Purusha Narayana desired, 'Would that I overpassed all beings ! would that I alone were
everything- here (this universe) !' He beheld this 'five days' sacrificial performance, the
Purushamedha and took it and performed offering therewith ; and having performed
offering therewith, he overpassed all beings, and became everything here. And, verily, he
who, knowing this, performs the Purushamedha, or who even knows this, overpasses all
beings, and becomes everything here."

Lord Shiva is Veda-Purusha as confirmed in the Taittiriya Aranyaka 10:24:1 "purusho vai

rudrah" means Lord Shiva is (Veda) Purusha.

Thus Vedas says that Narayan Rishi due to his devotion and Non-Dual Knowledge of
"Purusha" he becomes identical with Purusha(Shiva). Moreover this Narayan Rishi was
Mantra-Drsta(Seer) of the Hymn Purusha-Suktam. Now let's see even Upanishad(s) confirms
that Vishnu is Great Devotee of Mahadeva.

Lord Vishnu the Foremost Shaiva as per Upanishad.

We had seen that Vishnu Worships Shiva in Vedas and now Upanishads too Convey the
same. In the Upanishads it is said that Vishnu became All-Pervading due to Grace of Lord
Omkareshwar(Shiva).

“sarvakaraNAni manasi saMpratiShThApya dhyAna.n viShNuH prANaM manasi saha

karaNaiH saMpratiShThApya dhyAtA rudraH prANaM manasi sahakaraNairnAdAnte
paramAtmani saMpratiShThApya dhyAyIteshAnaM pradhyAyitavya.n sarvamidaM
|” (Atharvashika Upanishad 2:1 )

“The pranava (the sound of Om) makes all the souls to bow before it. It is the one and only
one which has to be meditated upon as the four Vedas and the birth place of all devas. One
who meditates like that goes away from all sorrows and fears and gets the power to protect
all others who approach him. It is because of this meditation only that Lord Vishnu who
is spread every where, wins over all others. It is because Lord Brahma controlled all his
organs and meditated upon it, he attained the position of the creator. Even Lord Vishnu ,
parks his mind in the sound (Om) of the place of Paramathma (ultimate soul) and
meditates upon Eeshana, who is most proper to be worshipped. All this is only proper in
case of Eeshana”.

Thus Upanishads too confirms that Lord Vishnu is Foremost Devotee of Lord Shiva. The
Vedas and Upanishad are considered as "Shruti" and Shruti Clearly mentions that Lord
Vishnu is adherent Devotee of Parvati-Pati. Due to this reason Lord Shiva is also
called "hari-vallabh

Lord Vishnu is Dear Devotee of Lord Mahadeva as per Itihasa.

The Itihasa are also treated as 5th Veda. And thus Itihasa is considered as much important
Scriptures. Regarding this, Mahabharata confirms that Sri Krishna is great Devotee of Lord
Sada-Shiva.

The below verse has been spoken by Veda-Vyasa in Mahabharata.

“sa eṣa rudra bhaktaś ca keśavo rudra saṃbhavaḥ | sarvabhūtabhavaṃ jñātvā liṅge ‘rcayati
yaḥ prabhum | tasminn abhyadhikāṃ prītiṃ karoti vṛṣabhadhvajaḥ |” (MBH 7:172:89-90)

“Kesava is that devoted worshipper of Rudra who has sprung from Rudra himself. Kesava
always worships the Lord Siva, regarding his Linga emblem to be the origin of the universe.
The God having the bull for his mark cherisheth greater regard for Kesava”.

Thus, Ved-Vyasa confirms that Sri Krishna is Great Devotee of Lord Pashupati.

The below verses has been spoken by Bheeshma in Mahabharata.

“rudrabhaktyā tu kṛṣṇena jagadvyāptaṃ mahātmanā।taṃ prasādya tadā devaṃ badaryāṃ

kila bhārata॥ 10arthātpriyataratvaṃ ca sarvalokeṣu vai tadā।prāptavāneva rājendra
suvarṇākṣānmaheśvarāt॥ ” (MBH 13:14:10-11)

“It is in consequence of the devotion of the high-souled Krishna to the illustrious Rudra
whom he gratified. O Bharata, in the retreat of Vadari, by penances, that he (Krishna) has
succeeded in pervading the entire universe. O king of kings, it is through Maheswara of
celestial vision that Vasudeva has obtained the attribute of universal agreeableness,–an
agreeableness that is much greater than what is possessed by all articles included under the
name of wealth“.

“yuge yuge tu kṛṣṇena toṣito vai maheśvaraḥ।bhaktyā paramayā caiva prītaścaiva

mahātmanaḥ॥” (MBH 13:14:13)

“In every new Yuga has Krishna (by such penances) gratified Mahadeva. In every Yuga has
Mahadeva been gratified with the great devotion of the high-souled Krishna“.

Here Bheeshma-Pitamah too agrees that Sri Krishna is Great Devotee of Lord
Trayambak(Shiva).

Not Only this he also says that In every new Yuga Lord Shiva is adored by Sri Krishna. And
we already know that In every yuga Incarnation of Sri Hari Vishnu worships Mahadeva.

Lord Vishnu and his most of his incarnation worships Lord Shiva, thus in Mahabharata
Bheesma said it and Ved-Vyasa recorded this.

Vishnu worships Mahadeva sincerely, with Pure Devotion, and utmost Faith due to which
Lord Omkareshwar(Sada-Shiva) also declares Lord Sri Vishnu as the Greatest Shaiva and this
is recorded in the Mahabharata and even in Puranas.

The following are the verse spoken by Lord Shiva himself

“satyaśaucārjava tyāgais tapasā niyamena ca | kṣāntyā bhaktyā ca dhṛtyā ca buddhyā ca
vacasā tathā | yathāvad aham ārāddhaḥ kṛṣṇenākliṣṭakarmaṇā | tasmād iṣṭatamaḥ kṛṣṇād
anyo mama na vidyate |” (MBH 10:7:60-61)

“With truth, purity, sincerity, resignation, ascetic austerities, vows, forgiveness, devotion,
patience, thought, and word, I have been duly adored by Krishna of pure deeds. For this
there is none dearer to me than Krishna”.

Thus even Itihasa and Veda-Vyasa too Consider Lord Vishnu as the best Shaiva ever in the
History and even no one can replace Devotion of Lord Vishnu towards lotus-feet of Uma
Maheswara

Lord Vishnu is best Shaiva as per Puranas.

Not Only Veda-Upanishad and Mahabharata but even Puranas celebrate the bhakti of
Lord Vishnu as the Purest Form and Vishnu as foremost devotee of Lord Shiva. In
above verse as per Mahabharata Shiva clearly says that due to extreme unconditional
devotion and affection of Vishnu(Krishna) no one is dear to him other then Vishnu.

The Very same thing is narrated by Lord Shiva in Shiva Maha-Purana. Let's see.

“īśvara uvāca | vatsaprasanno ‘smi hare yatastvamīśatvamicchannapi satyavākyam |

brūyāstataste bhavitā janeṣu sāmyaṃ mayā satkṛtirapyalapthāḥ ||31 itaḥ paraṃ te
pṛthagātmanaśca kṣetrapratiṣṭhotsavapūjanaṃ ca ||” (Shiva Purana 1:7:31-32a) “[Ishwara
said:] Hey dear son Vishnu! I am highly pleased with you because even though you were
desirous of gaining lordship (superiority) you remained a speaker of truth (didn’t lie to
achieve victory); for this reason you would gain the lordship on this universe and you would
gain equality with me and even would be honoured by me. From this day separate idols of
yours would get established in various shrines and you would receive worship”.

Now the same is mentioned by Lord Vishnu in the Padma-Purana. In Padma-Purana Lord
Vishnu also says that he contemplating(meditating) on Lord Shiva. Thus in Padma-Purana
Lord Vishnu says the following words to Mother Lakshmi-Devi. Note that the below words
were spoken by Lord Vishnu himself to his dear consort in response to inquiry of Lakshmi-
Mata.

“śrībhagavānuvāca |
nāhaṃ sumukhi nidrālurnijaṃ māheśvaraṃ vapuḥ |
dṛśā tatvānuvarttinyā paśyāmyaṃtarnimagnayā ||” (Padma Purana:UK:175:7)

“[The lord said]: O you of beautiful face, I’m not sleeping, rather, by the vision which sees
(follows) the truth, I am contemplating by being fixed (nimagna) in my true form of
lord Maheshvara (lord Shiva)".
The Very same thing is confirmed in the (Atharvashika Upanishad 2:1) and same is being
repeated by Lord Vishnu in Padma-Purana. Shiva-Purana too mentioned the same concept
of Upanishad and Veda.

Sri Rama himself says the following Verse in the Valmiki Ramayan.

Valmiki Ramayan, Yudhha Khanda, Sarga 123 Verse 19

एतत् कुक्षौ समु दर् स्य स्कन्धावारनिवे शनम् || ६-१२३-१९

अत्र पूर्वं महादे वः प्रसादमकरोत्प्रभु ः |
"See this island, located in the middle of the ocean, where my troops were stationed. At this
place,  the lord Shiva (the supreme deity) formerly bestowed his grace on me."