paying it forward
The act of repaying a kindness received by doing good for someone else, rather than directly to the original benefactor.
In the spirit of paying it forward, I helped someone in need.
He repays the kindness he received by paying it forward to society.
Compound of 恩 (おん, 'kindness, favor') and 送り (おくり, 'sending'). The term describes the concept of forwarding a good deed to others instead of returning it directly.