It is written in the sefer Siach Sarfei Kodesh: The Rebbe Reb Bunim was learning with his students. Amongst them was Reb Hersh Temishvar. He was one who would listen intently, but never once did he ask or answer anything.
One day, the other students came over to Reb Hersh and informed him of the new policy: If he wouldn’t contribute anything to the class, he would be asked to leave.
They were learning that day the portion in Gemora Kiddushin (Daf Yomi: 13a)dealing with the question of where is the source that teaches us that the husband’s death completely permits the wife to remarry.
The Kotzker Rebbe asked his students: Why can this not be derived from the fact that Dovid HaMelech married the wife of Naval after he died? If the husband’s death does not allow the wife to remarry, how could Dovid have married her?
Reb Hersh spoke up and answered as follows: It would not be a proof from that incident, for Naval was considered a rebel against Dovid’s Kingdom, and therefore all of his possessions legally belong to Dovid. Accordingly, even if we would say that a husband’s death would not permit the wife to remarry, Dovid would still be permitted to marry his wife, for he is the owner of all of Naval’s possessions. We would have thought that Naval’s wife would have been included in his possessions, and that would have allowed Dovid to marry her.