Yes.
Righteous people give without sparing. God rewards those who give to the poor by making sure the givers lack nothing. If you invite guests over for a meal, never invite your friends and relatives; only invite poor and disabled people.1 One of the requirements to gain eternal life is to sell everything you have and give the money to the poor. If you do that, you will be perfect, and God will reward you in heaven. Even if you’re poor yourself, you must work your way out of poverty, just so you’ll have something to give to the poor.
But if you refuse to listen to the pleas of the poor, your own pleas will be ignored and you will be plagued with curses. If you ever keep anything to yourself when poor people want it, the love of God is not in you, and you deserve to lose an arm.
No.
Giving to the poor isn’t always the right thing to do. Sometimes there are more important things to do with your valuables than give to the poor. And if you do give, you don’t have to give without sparing. Only give what you can spare, and only give what you really want to give. And if you do give everything away, don’t give it all to the poor. You have to give to anyone who asks you for something, so you’ll have to save some for the non-poor askers too.