Responsa for Kiddushin 55:19

Q. A traded his horse with B for wine, and B received the horse. Before B shipped the wine to A, a Gentile claimed that the horse had been stolen from him, and took it away from B. Now B refuses to ship the wine to A, claiming the transaction was made in error.
A. As soon as B received the horse, the wine became A's property, and B cannot retain it. If A claims that his horse was not a stolen horse and that the Gentile took it away unjustly, or that he (A) had no knowledge that it was a stolen horse, he is not responsible (since we cannot rely on the Gentiles' word). If, however, B can prove that at the time of the transaction A knew that it was a stolen horse and that the Gentile had a right to take it, B may keep his wine.
SOURCES: Cr. 186; Pr. 35; Tesh. Maim. to Kinyan, 6; Mord. B. M. 298.

Q. A rich man called the son of a worthy and scholarly family "bastard, son of bastards". What should be his punishment?
A. The Talmud prescribes thirty-nine lashes, and the judges may punish him more severely, if he makes a practice of offending people. The punishment should also depend on the high qualifications of the man and the family insulted. But for his own salvation, he should fast, chastise himself, give charity to the poor, and ask the Lord for mercy and forgiveness; for he has offended scholars in their graves which is, indeed, a serious sin.
SOURCES: Cr. 285; Pr. 132; Rashba I, 855; Mord. B.K. 105. Cf. Weil, Responsa 28.