The "Golden Rule" or "ethic of reciprocity" is a moral maxim or principle of altruism found in many human cultures and religions.

Christianity:
Mark 12:30-31, Jesus answer to the phrases who were trying to trick him into saying something that would cause people to turn against him. They asked what is the greatest commandment? Jesus said,
" 'Love the Lord your God with all your heart and with all your soul and with all your mind and with all your strength.' (Deut 6:4-5.) The second is this: 'Love your neighbor as yourself.' ( Lev 19:18.) There is no commandment greater than these."

Islam:
"None of you [truly] believes until he wishes for his brother what he wishes for himself." Number 13 of Imam "Al-Nawawi's Forty Hadiths."

Hindusm:
This is the sum of duty: do not do to others what would cause pain if done to you." Mahabharata 5:1517

Buddhism:

• "...a state that is not pleasing or delightful to me, how could I inflict that upon another?" Samyutta NIkaya v. 353
• Hurt not others in ways that you yourself would find hurtful." Udana-Varga 5:18

Links:
Versions of the Golden Rule in dozens of religions and other sources
Golden Rule - Wikipedia