You cannot teach a person to be unselfish. You can’t be forced to be unselfish, nor can you frame laws to punish selfishness.
The way you can spread unselfishness is by making it a culture, a culture within society.
Since you can’t teach a person to be unselfish, the best you can do is spread unselfishness as a trait for people to imbibe.
As a leader, you can spread the good by not showing the good that you do, but by seeing and showing the good that others do. And then the others seeing the good that many others do. Till the circle of all seeing what good all others do is complete.
You don’t become unselfish by showing your unselfishness, but by seeing the unselfishness of others and spreading it!