Halakhah su Deuteronomio 23:21

Charity comes within the general class of vows. Therefore, if one says, "I vow a Sela⁴A coin worth two common Shekels. to charity," or, "I vow this Sela to charity," he must give it to the poor immediately; and, if he delays, he is guilty of transgressing the precept, "Thou shalt not slack to pay it,"¹Deut. 23:21. since he has the money and poor people are a-plenty. But if no poor are available, he should separate the money and lay it aside until he meet one.
RMI.—He transgresses a law in delaying payment, only when he vows to give charity which he himself must distribute. But if he vows to contribute to the general charity fund in the synagogue and the like, which must go through the hands of the Gabbai, he does not transgress the precept, although poor are a-plenty, until the Gabbai asks for it; and then, if he delays, he is a transgressor. And if the Gabbai does not know of the vow, he must inform him how much he vowed, so that he might come to collect.
That he must not delay in paying his vows to charity refers to vows as ordinarily made; but, of course, a man is permitted to separate a sum of money which he himself is to distribute a little at a time as he may see fit. And so also, if he stipulates a condition in making the vow, that the Gabbaïm should be permitted to exchange the money for gold, then they are permitted to do so.

To lend to the gentile with interest: That we were commanded to request interest from the [other] peoples when we lend to them and that we not lend to them without interest. And about this is it stated (Deuteronomy 23:21), "Take interest from the foreigner." And likewise is it permitted to borrow from them with interest. And they said in Sifrei, "'Take interest from the foreigner' - that is a positive commandment; 'and from your brother, do not take interest' - that is a negative commandment."