It depends upon circumstances. If his debtor is able but refuses to pay, there is nothing in Christ's meaning to prevent the Christian from appealing to law to recover what is justly his, after all peaceable means have failed. The Revised Version of Luke 6:35 reads, "Lend, never despairing" (margin, "despairing of no man"). We are to be kind to those of whom we can expect no return in sort. God will repay us, though man does not. "It is meant of the rich lending to the poor a little money for their necessity to buy daily bread or to keep them out of prison; in such a case we must lend with the resolution not to demand interest for what we lend, as we may most justly from those that borrow money to make purchases withal or to trade with; but that is not all, we must lend though we have reason to suspect that what we lend we lose; lend to those who are so poor that it is not probable they will be able to pay us again. This precept will be best illustrated by that law of Moses (Deu. 15:7-10) which obliges them to lend to a poor brother as much as he needed, though the year of release was at hand." - This is an old commentator's explanation, but it is good and true.