At times I've read bumper stickers and the like quoting Thomas Paine:

The world is my country, all mankind are my brethren, and to do good is my religion.

It's a good sentiment: anti-nationalistic, valuing everyone everywhere, valuing helping people. I got into looking for the source, though, and the actual source is Chapter V of his 1792 Rights of Man:

In stating these matters, I speak an open and disinterested language, dictated by no passion but that of humanity. To me, who have not only refused offers, because I thought them improper, but have declined rewards I might with reputation have accepted, it is no wonder that meanness and imposition appear disgustful. Independence is my happiness, and I view things as they are, without regard to place or person; my country is the world, and my religion is to do good.

I've emphasized the bit that the common quotation is derived from. It doesn't have the explicit statement of brotherhood, but isn't that far removed.

I haven't read all of his Rights of Man, which is slow going because its deep into issues I'm not familiar with and the language is old, but reading some of it one thing that stuck out is that he's very aware of distribution issues, and how taxes can hit the poor much harder than the rich. He notes, for example, that rich people can avoid the tax on beer brewed for sale because the rich have their own brewed for them. He also notes that taxes on land have stayed constant while consumption taxes have risen dramatically, to where beer taxes are now higher than land taxes. He proposes to fix this with a graduated wealth tax, increasing the marginal tax per pound gradually as total wealth rises.