Responsa על בכורות 104:16

Q. The bishop imprisoned B in order to extort money from him. B said to A: "You owe me eight marks, give five marks to the bishop". Meanwhile a rich Jew promised to speak to the bishop on B's behalf and assured B that he would thus effect his release. A, however, gave five marks to the bishop and B was released. Now B demands that A repay him the full eight marks.
A. A is under no obligation to repay the five marks to B since he carried out a direct order to pay this amount to the bishop. Moreover, had A acted on his own initiative and ransomed B without being requested to do so, he would still have been entitled to reimbursement, for a Jew should be ransomed even against his express will, and may be charged with the expenses thus incurred. The promise of the rich man to speak to the bishop was of no consequence, since he did not offer to spend money on B's behalf. We know that mere words are of no avail. The Gentiles are not moved by words, only money affects them. Those who fall into their hands have no hope for deliverance save through the payment of ransom.
This Responsum is addressed to Rabbi Haim Paltiel b. Jacob.
SOURCES: Cr. 32–3; Tesh. Maim. to Nezikin, 17. Cf. Maharil, Responsa 78.