The phrase "selfish interest" refers to when someone only thinks about themselves and what benefits them, without considering others. It means putting your own wants and needs above everyone else's. Full definition
Well then you're putting your own selfish interest above the people's interests. (politico.com)
All the party leaders must work together, so our working together and their visits to my office were not for selfish interest or about our ambitions alone. (punchng.com)
While becoming, each is purely concerned with selfish interests, seeking «only the satisfaction of its own subjective aim...» (43). (religion-online.org)