Avos d'R' Nasan, 33:1:
… Not only that, but our father Abraham did tz'daka (≈social justice) first and thereafter mishpat (≈justice), as is said [Gen. 18:19] "for I know him, for he will command his sons and family after him to do tz'daka and mishpat". When two litigants would come before our father Abraham in a matter of judgement, and one [of them] would say about his fellow "he owes me a mane", our father Abraham would take out a mane of his and give it to [the defendant] and tell them "arrange your case", and they arranged their cases. If [the] one was found liable to his fellow, [Abraham] would say to the one holding the mane [he had given him] "give the mane to your fellow"; if he was not [found liable], [Abraham] would tell them "split [the mane] and depart in peace".
But King David did not do thus; rather he would do mishpat first and thereafter would do tz'daka, as is said [Ⅱ Sam. 8:15] "David would do mishpat and tz'daka for all his nation". When litigants would come before King David for judgement, and one [of them] would say "he owes me a mane", [King David] would tell them "arrange your case" and they would arrange their case. If [the] one was found liable to his fellow for a mane, [King David] would take out a mane if his own and give it to him; if not, he would tell them "depart in peace".
It seems like anyone who knew about this policy of Abraham's or of David's could simply refuse to pay his debts, or could steal or damage property, or the like, and know that the damages will be paid for him. With that in mind, how do we explain these policies of theirs?