Skeptics occasionally assert that "Give to everyone who begs from you" supports modern government entitlement programs.

What has to be kept in mind is that the ancient world, unlike ours in the modern West, was collectivist in orientation -- people shared goods in common, for the common good. It did not mean anything like a modern governmental entitlement program or a secular welfare state. It was an instruction about community borrowing and social cohesion among an ingroup.

One thing to keep in mind here is that in the first century, if someone larger and stronger, or with a bigger club, took away your stuff, there wasn't a whole lot you could do about it. The Romans were too busy and/or apathetic to address such matters as petty crimes among the commoners...

You could fight back, or you could go find the crook and either haul him to the authorities yourself, or demand your stuff back ("ask" here carries the sense of demanding; more likely you're demanding your stuff back right after it is taken); and of course you'd start a fight in the process... and that's the point, and why Luke paired this saying with the one about the personal offense of cheek-smiting -- the point here is, don't escalate the violence. And that's the way a believer would have to do it, since there was no proper way for justice to be administered.

This leads to the slightly different element of Matthew 5:42. Read woodenly this would suggest giving away things without discernment, but the two parts of the verse are actually in Hebrew parallelism and are two ways of saying the same thing. "Ask" and "borrow" in Hebrew are synonyms in a certain sense: A difference is made in Hebrew between borrowing something tangible (a book or a coat) and borrowing something interchangeable (money, flour, etc). Jesus uses the two different senses in this verse: "Give to him that asketh thee (for a thing like a book or a coat), and from him that would borrow (flour or money) of thee turn not thou away."

But now pair this with the teaching in 5:39 on revenge. The teachings belong together: One way to "get even" with a neighbor would be to refuse to extend them a loan. In a corporate society such as the ancient world, such refusal to exchange or loan violated a common precept of survival and concern for the common good.