Responsa על כתובות 66:16

Q. A and B were captured and held for ransom. The former was rich and the latter, poor. A spent money with the help of his mother and effected the release of both A and B. A claims that B asked to be ransomed, and therefore demands that B pay his share of the expenses. B denies having asked to be ransomed.
A. A Jew should be ransomed even against his express will, and be charged with the expenses incurred. A captive in the hands of Gentiles is exposed to ruthless treatment and incessant flogging, and his very life is in danger. Therefore, anyone who effects the ransom of a Jew is praiseworthy and is entitled to the expenses incurred. Moreover, Jews threatened by a common danger may force one another to contribute of their means to the measures that will free them of that danger. A and B have to share the expenses in proportion to their wealth, since they were captured for the purpose of extorting money from them.
R. Meir adds that this question had already been sent to him from Magdeburg. He had also been asked concerning a tutor who was arrested because of a false accusation, and who requested his former employer not to ransom him. R. Meir's answer was the same.
SOURCES: Pr. 39; L. 345, cf. Mord. B. K. 58–59; Cr. 32–33; Am. II, 128; Tesh-Maim. Nezikin, 17. Weil, Responsa 148; ibid. 149; Moses Minz, Responsa 1.