It can be traced back to antiquity. The only well known case wich come to my mind right now is the help provided to Rhodes after the earthquake that destroyed the city and the mighty colossus in 227. In fact all the hellenistic kings that helped the little republic needed that the city was rebuilt. Indeed, because of it's quite neutral political position in the middle of the conflicting kingdoms and because of the importance of their trade fleet, the city was vital to the trade in the eastern mediterraniean in the IIIrd century.

I'm pretty sure that it should be possible to find other, earlier exemples but in any case there is always a particular reason to grant the help, political or even mythological (like mythical common ancestor).