What does Hinduism say about altruism. When learning about Hinduism in college level textbooks and other authoritative texts, altruism or service is not mentioned as a key tenet of the religion.
Service to others is integral to Hindu ethics.
Helping the indigent
Bhishma said, "Whatever wishes one entertains with respect to oneself, one should certainly cherish with respect to another. With the surplus wealth one may happen to own one should relieve the wants of the indigent. It is for this reason that the Creator ordained the practice of increasing one's wealth (by trade or laying it out at interest)."
Mahabharata, Santi Parva, Section CCLIX
Need to feel for the afflicted
A Brahmana might be even-sighted and calm in disposition. But if he cannot sympathise with the afflicted, all the merits of his austerity come to naught like water kept in a broken pot.
Srimad Bhagavata Purana IV.14.41
Image worship and service to humans
I abide in all beings as their inner-most soul. Disregarding My presence within them, men make a show of worshiping Me through images. If one disregards Me present in all as their soul and Lord but ignorantly offers worship only to images, such worship is as ineffective as a sacrificial offering made in ashes. A man who persecutes Me residing in others, who is proud and haughty, who looks upon God as the other – such a person will never attain to peace of mind. If a man disregards and persecutes fellow beings, but worships Me in images with numerous rituals and rich offerings, I am not at all pleased with him for proffering such worship. A man should, however, worship Me in images, side by side with discharging his duties, which include the love of all beings, until he actually realises My presence in in himself and in all beings. As long as man is self-centred and makes an absolute distinction between himself and others (without recognising the unity of all in Me, the Inner Pervader), he will be subject to the great fear of Death (including every form of deprivation of self-interest). So, overcoming the separateness of a self-centred life, one should serve all beings with gifts, honour and love, recognizing that such service is really being rendered to Me who reside in all beings as their innermost soul.
Srimad Bhagavata Purana III.29.21-27
Paropakaram Vahanti Nadya, Paropakaram Duhanti Gaaya, Paropakaram Phalanti Vriksha, Paropakaram Idam Shareeram’
Rivers flow for others to benefit, Cows give milk for others to benefit, Trees bear fruits for others to benefit, and similarly this physical body is also meant help others.”
Popular Subhashitani Neeti shloka that teaches selflessness , altruism
Nish-kama karma or karma yoga is the key principle of Bhagavad Gita, suggests that selfless action is the path for liberation
LokaSangraha is another key concept emphasized in Gita which means the universal well-being(welfare of the common good)
As ignorant people perform their duties with attachment to the results, O scion of Bharat, so should the wise act without attachment, Wishing the welfare of the world (Bhagavad Gita 3.25)
oṃ sarve bhavantu sukhinaḥ sarve santu nirāmayāḥ sarve bhadrāṇi paśyantu mā kaścidduḥ khabhāgbhaveta। oṃ śāntiḥ śāntiḥ śāntiḥ॥
May all sentient beings be at peace, may no one suffer from illness, May all see what is auspicious, may no one suffer. Om peace, peace, peace.
Brihadaranyaka Upanishad Shanti Mantra(1.4.14)
The word ‘dharma’ is from its (sanskrit) root ‘dhr’ which means. ‘to hold’ or ‘to support’. Therefore, ‘dharma’ means that which holds up or supports the grand order of God's manifestation. With this understanding of dharma , the moral rules of conduct, and duties proposed by Hindu scriptures, motivates one towards altruism.
शरीरमाद्यं खलु धर्मसाधनम् sharIramAdyaM khalu
(Sarga 5:33 of Kumarasambhavam by Mahakavi Kalidasa)
Only when you have healthy body and mind, you can perform your dharma
(Motto of AIIMS)
So the very purpose of maintaining a healthy body is to aid in performing one's dharma (not to pursue any selfish desires.)
The injunctions , aphorisms of Hindu scriptures seem to recommend the attitude of altruism, in the context of dharma.
The concepts of dana ( charity) and sewa (service) is an integral aspect of the fundamental tenets of hinduism.