I like this passage from George Foot Moore's, Judaism In The First Centuries of the Christian Era, The Age of the Tannaim, from Chapter 7 of Volume 2, Public and Private Charity. He's dealing with the Jewish understanding of God's laws of charity, which are quite extensive.
When I first started studying the Jewish background of the New Testament, (Jesus was Jewish, attended synagogue, taught from the Hebrew Bible, was called rabbi by his disciples, spoke Hebrew.), the most surprising thing was the importance of charity in Judaism. I'd had the impression that caring for others was one of the distinguishing characteristics of Christianity, but Christianity's care for the needy, at least as Christianity has come down to us, is a weak, diluted, version of Judaism's. When Jesus says, as Moore quotes below, "42 Give to the one who asks you, and do not turn away from the one who wants to borrow from you." (Matthew 5:42 NIV) he's quoting a requirement of the Jewish law. Jews were to lend to fellow Jews when asked, at zero interest. It's my understanding that even today, at least some synagogues, have interest free lending facilities for their members. Hallelujah. Jesus wasn't making a suggestion, this was a commandment. Well… but that wouldn't be practical. Exactly. So that lets us off.
Anyway, read the the passage below, but here's the part that I liked, "The donor, who owes God all he has, becomes a creditor of God — if it was not so written in Scripture, no one would venture to say such a thing!"
The promise of God's blessing on the benevolent (vs. 10) includes not only the man who gives for the relief of the poor but one who solicits others to give; and if, unable to give anything else, he expresses his sympathy in words, that too has its reward.2 On the other hand, warning is given that the poor man refused an alms may cry to the Lord against him who refused him, * and it will be sin in thee.' Sin it is in any case, but God will be quicker to punish when the unfortunate cries to him.
It will no doubt have occurred to the reader that most of this fine doctrine about charity is interpreted into the text, not out of it. And that is precisely the thing to be observed about it. The fundamentals of Jewish teaching on the subject from a far earlier time are here ingeniously worked into a single passage only a few verses long.
Parallels to them all can be adduced in multitude.3 When Jesus said: 'Give to him who begs of thee, and do not turn away him who wants to borrow from thee' (Matt. 5, 42), it is not, like the preceding injunctions of non-resistance, what the Jews called conduct that keeps "inside the line,"4 but an exact summary of what they laid down as prescribed by divine law.
To lend to a would-be borrower is not optional but obligatory,5 and no less obligatory to give to the poor according to the measure of his need and to the ability of the giver.6 One should not withhold the needed relief out of apprehension that if he distributes all his property to others he may himself be reduced to want and come to be a charge on the community; he should trust the promise of Deut. 15, 10b — if he does his part, God will do His. He has the best of security, for 'he who befriends the poor lends to the Lord, and He will repay him for his good deed' (Prov. 19, 17).1 The donor, who owes God all he has,2 becomes a creditor of God — if it was not so written in Scripture, no one would venture to say such a thing!3 God says to Israel: "My sons, whenever you give food to the poor, I impute it to you as though you gave me food, as it is said, 'my offering, even my food for my fire sacrifice' (Num. 28, 2). Does God eat and drink! Nay, but whenever you give food to the poor I impute it to you as though you gave me food." 4