The warranty period for slaves is four nights

It is narrated from Sayyiduna Uqbah bin Amir (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "The option to return a slave is four nights."
This hadith has a sahih (authentic) chain, but it is mursal, because Imam al-Hasan al-Basri did not hear from Sayyiduna Uqbah bin Amir (may Allah be pleased with him); and it also has a supporting narration (shahid).

It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that Habban bin Munqidh (may Allah be pleased with him) was a weak man, and he had received a deep head wound that had reached the membrane of the brain. So the Messenger of Allah (peace and blessings be upon him) granted him an option of three days in anything he bought. His tongue had a stammer, so the Messenger of Allah (peace and blessings be upon him) said to him: "When you trade, say: 'La khilabah' (There is to be no deception)." The narrator said: I used to hear him say (because of his stammer): "La khidhabah, la khidhabah." He would buy something and bring it to his family, and they would say: "This is expensive," and he would reply: "The Messenger of Allah (peace and blessings be upon him) has given me the option (to return) in my sales."