There are four temperaments, etc.: the one who says "what is mine is mine, and what is yours is yours" He is not generous, but he is good in that he 'hates presents.' And it is difficult. As how can they say that this is an [average] temperament? And is not someone who prevents himself from giving charity completely wicked? And [granted] that it is true that according to the one that says that it is the temperament of Sodom, it comes out well - as it is stated (Ezekiel 16:49), "Behold this was the sin of your sister, Sodom, etc.; she did not support the poor and the needy." Rather, it is dealing with one who gives charity from fear of God, however his nature is to be stingy. And hence since he 'supports the poor and the needy,' what does his nature matter to us - the actual temperament (in practice) is [average]. "And some say that it is the trait of Sodom" and that its source is very bad, since his nature is to be stingy. But [regarding] if he 'does not support the poor and the needy at all,' everyone agrees about this that he is completely wicked and that it is the temperament of Sodom.
"what is mine is yours, and what is yours is mine" - [that's an] am ha'arets (literally, a man of the land): Because this one wants the improvement of the world, he is called a man of the land. As he wants to give and to take, since love increases among them through this. And even if this is a good trait for the improvement of the world, this is not from wisdom. As one who 'hates presents shall live.' And the good temperament is to give but not to take.
WHAT’S MINE IS YOURS AND WHAT’S YOURS IS YOURS—THIS IS A PIOUS PERSON. Not that he gives away all he owns, for the Sages say (Ketubot 50a) that even one who gives freely should not give more than a fifth of what he has in order that he not give too much and be forced to depend on others. Rather, the mishna is discussing one who gives the proper amount—Maharal in Derech Chaim.