Sanātan Dharm Principle
Sanātan Dharm is a phrase used to refer to the right way of conduct but on a general note it refers to Hinduism. The reason why it has been applied as a synonym to 'Hindu Dharma' is because the phrase itself reflects eternal, universal ethics or "laws." The phrase perhaps goes as far back as Atharva Veda wherein in Hymn XCI it mentions the "eternal Law" and "eternal order". It is also mentioned in the Bhagavad Gitā as "Sanātanah Dharme", when Krishna says he is the basis of “"eternal dharma"” and when Arjuna calls Krishna "the protector of the Eternal Religion" is noted in the Bhagavad Gitā. The idea of a "protector of the eternal religion" has been taken up by the Swaminārāyan Sampradāy which uses the phrase Sanātan Dharma Sanrakśak. Krishna in the Bhāgvat Purana says that he incarnates when the Sanātan Dharm is misused (or misunderstood.) Narada Muni proclaimed that he learned all about the Sanatan Dharm from the rishi Narayan (brother of Nara) himself. Devahuti (mother of Rishi Kapila) had called Krishna sad-dharma-vidāṁ (“knower of the Eternal Religion.”) Even certain Hindu sects use the phrase 'Sanatan Dharma' or a version of it in a different language. For example the Bon religion uses the phrase 'Yungdrung Bon' which literally means Eternal Religion. Jainism too has used the phrase 'Eternal True Dharma'.
In Sanatan Hindu Dharm
Compassion and charity
Charity is considered as a virtue in religion that rewards good karma to the generous giver. It is one of the 10 niyamas. Both Dāna and dayā are expounded by Patanjali to the asuras to civilize them. Kama is to be conquered by dama or self-control, krodha is to be overcome by dayā or compassion and lobha or greed by dāna or gifts. In the "Pativratya-mahatmya Parva" of the Mahābharata, in the "Vara Parva, "Savitri is following deva Yama into the beyond and he is taking away Satyavan. Yama asks her to stay back. She says: Where my husband is being taken, or where he goes, I should follow him. This is the Sanātan Dharma. A little later when she pursues her path and Yama asks her to return, she says, "Compassion and charity are the Sanātan Dharma."
Compassion for others goes to the extent of respecting the proper burial of adversaries. In Ramāyaṇa of Valmiki, the rakṣasa Virādha says to Rama to give his body a proper burial because it is the Sanātana Dharma to give a rakṣasa such.
Truthfulness is one of the Panchavratas or Five Vows prescribed in religion, and its importance is reiterated by the scriptures connecting truth with religion. The Manu Smṛti declares, "Speak truth that is pleasant. Never speak truth that is not pleasant. Don't speak a lie, even if it is pleasant to hear. This is the Sanātan Dharma." The "Shanti Parva" of the Mahabharata declares, "It is good to speak truthfully; better still to speak truthfully; better still to speak what may benefit others. This is the Sanātan Dharma."
The ‘Churning of the Lake’ on Mt. Mandara as it is called was a tug-of-war competition to win the Amrita nectar.
After the Asuras lost the game, there were still many among them that demanded the nectar. Some of them began saying that they should honour the agreement with the Devas, which they won fairly.
- devāḥ svaṁ bhāgam arhanti
- ye tulyāyāsa-hetavaḥ
- satra-yāga ivaitasminn
- eṣa dharmaḥ sanātanaḥ
- iti svān pratyaṣedhan vai
- daiteyā jāta-matsarāḥ
- durbalāḥ prabalān rājan
- gṛhīta-kalasān muhuḥ
- - Bhāgvat Purana 8.8.40
In Bauddh Dharm
Although Buddha usually spoke of the Sanātan Dharma, he sometimes used other synonymous terms for "Sanātan Dharma," such as "Akaliko Dharma," and "Poranako Dharma."
The Buddha himself had used the term 'scholarship' when referring to the masters of the pure Sanātan Dharma: "Sanatanam va panditanam dhammo" or ''Scholarship is the Sanātan Dharma."
Actually Lord Buddha said, "Truth is Nirvana's speech. This is the Sanātan Dharma."
- P. 336 Hymns of the Atharva Veda By Ralph T.H. Griffith, 
- "Bhagavad Gitā" 14.27: “"I am the basis of the formless Brahman, the immortal and imperishable, of eternal dharma, and of unending divine bliss."”
- "Bhagavad Gitā" 11.18
- catur-yugānte kālena
grastāñ chruti-gaṇān yathā
tapasā ṛṣayo ’paśyan
yato dharmaḥ sanātana
- Bhāgvat Purana 8.14.4
- śrī-nārada uvāca
natvā bhagavate ’jāya
vakṣye sanātanaṁ dharmaṁ
- Bhāgvat Purana 7.11.5
- taṁ tvā gatāhaṁ śaraṇaṁ śaraṇyaṁ
jijñāsayāhaṁ prakṛteḥ pūruṣasya
- [Bhāgvat Purana 3.25.12]
- Sutrakritanga, Book 2, Lecture 1; P. 351 The Sacred Books of the East, Volume 45 edited by Friedrich Max Müller
- Charity means Dāna.
- Niyamas means essential customs for human mokśa.
- Asuras means demons.
- P. 271 The Vedanta Kesari, Volume 83, Issue 2, By Sri Ramakrishna Math
- Ramāyaṇa 3.2
- Rakṣasa means demon.
- P. 49 Rāmāyaṇa: The forest. Book three By Vālmīki
- Manu Smṛti 4.138
- "Satyam bruyat priyam bruyan/na bruyat satyam priyam/priyan ca nanrtam bruyad:/esa dharmah sanatanah,"
- Agnihotra means marriage ceremony.
- P. 308 Essays in Classical and Modern Hindu Law: consequences of the intellectual exchange with the foreign powers By John Duncan Martin Derrett
- Ramāyaṇa 21.10
- His father was King Dasharatha.
- P. 151 Rāmāyaṇa: Ayodhyā. Book two By Valmiki
- Ramāyaṇa 55.15
- He would banish his son due to the promised favor to Kaikeyi.
- P. 321 Rāmāyaṇa: Ayodhyā. Book two By Valmiki
- Rāmāyaṇa 27.30
- P. 181 Rāmāyaṇa: Ayodhyā. Book two By Valmiki
- "Na hi varena verani, sammantidha kudacanari/ Averena ca sammanti, esa dhammo sanantano," P. 50 Rediscovering Gandhi By Anil Dutta Mishra
- Sutta Nipata, Vagga 3, Sutta 3 , P. 106 Buddha`S Teachings Being The Sutta-Nipata Or Discourse Collection edited by Lord Chalmers