Musannaf Ibn Abi Shaybah

Hazrat Hisham (may Allah have mercy on him) narrates that Hasan (may Allah have mercy on him) said regarding a prisoner in the custody of the enemy: If he gives a gift to someone or gives something to someone of his own will, and makes a bequest of one-third of his wealth, then it is permissible.

Hazrat Ibn Abi Dhi'b (may Allah have mercy on him) states that Imam Sha'bi (may Allah have mercy on him) said: It is permissible for a prisoner to make a bequest of only one-third of his wealth.