Supporting the poor not only helps the poor person, but also the giver. Before strict heavenly judgment comes to the world, God grants a gift to someone he loves – the opportunity to support a poor person. Then, when the judgment does come, this mitzva serves as a protection and shield from harm.

When the Holy One, blessed be He, loves a person He sends him a gift. Who is that? It is a poor person, so the one God loves can gain merit through him. Once he gains the merit [of giving to the poor], he draws special divine favor from the “right side” [of divine loving-kindness], God spreads it over his head and marks him [for good]. When strict divine judgment comes into the world, the destroyer [sent by God] will be careful not to harm him, for the destroyer will raise his eyes, see that mark, and leave him [unharmed]. This is why the Holy One, blessed be He, presented him in advance with the poor person so as to be able to gain merit through him. (Zohar 1:104a)

The Torah commands us to lend money to the poor. The world seems to have those destined to lend money and others destined to borrow. Why isn’t wealth distributed equally? Why doesn’t God give the poor their sustenance directly? In fact, in this way God acts toward us with great kindness – for someone who lends money to the poor has the opportunity to develop a loving and giving character. This makes him fitting to receive divine goodness.

God wanted the people He created to learn and become accustomed to the praiseworthy traits of kindness and mercy. By improving themselves with good character traits they become worthy of receiving divine goodness…. If not for this goal, He, may He be blessed, could have provided for the poor without involving us. Rather, it was out of His kindness, may He be blessed, that we were made His agents [to help the poor] in order to bring us merit. (Sefer HaĤinnukh, Mitzva 66)

Further reading: For the anecdote about Rabbi Akiva’s daughter, who gave charity on the night of her wedding and was saved from death, see A Concise Guide to the Sages, p. 426.

The rich person who gives charity gains more than the poor person receiving it. The poor benefit in this world through receiving charity, but the rich, by giving, benefit through reward in the next world.

How much greater is the benefit that the rich receive through giving charity to the poor than anything that the poor can receive from the rich! For what the poor receive from the rich only lasts during their time in this world, but the rich benefit through their merit in the World to Come. (Rabbeinu Baĥya ibn Ĥalawa, Kad HaKemaĥ, Tzedaka)

When a person gives to another he merits receiving a flow of [divine] influence from above. God is the source of all goodness, and He grants wealth to all who give charity and bestows upon others that which was given to them.

Giving charity involves directing a flow of generosity toward other people. Anyone who does this is assisted by God, may He be blessed, from above. How does the Holy One, blessed be He, help him? Through giving him money that he can direct in a flow [of generosity toward others]. This is because one who bestows on others is like a spring. For just as a spring sends forth its waters far away, so too, a person bestows a flow of goodness on others. Therefore, God, may He be blessed, who is the [ultimate] source sending His flow of goodness to all life, directs that flow toward this person who will then direct it onward to others. Just like the waters of a spring flow outward, and the source of the spring sends forth more so there will be no lack of water – and the further out it sends water, the more water will be replaced – [so too, the more charity one gives, the more wealth God will send toward him]. But if the spring does not flow outward, the source will not give water. (Maharal of Prague, Netivot Olam, Netiv HaTzedaka 1)