Sayyiduna Abdullah bin Zubair (may Allah be pleased with him) says that when the Messenger of Allah (peace and blessings be upon him) would perform the Isha prayer, he would offer four rak'ahs and also perform one rak'ah of Witr, and then he would sleep. Later in the night, he would perform his (additional) prayer.

It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with him) that he performed two rak'ahs with the Noble Prophet (peace and blessings be upon him) in his house after the 'Isha prayer.

It is narrated from Sayyida Aisha (may Allah be pleased with her), she says that after leading the people in the Isha prayer, the Prophet (peace and blessings be upon him and his family) would come to my house and perform two rak'ahs, and during the night he would offer (9) rak'ahs including the Witr prayer.

Shuraih bin Hani says: I asked Sayyida Aisha (may Allah be pleased with her) about the prayer of the Prophet Muhammad (peace and blessings be upon him). She said: When you were engaged in conversation, there was no prayer more appropriate to delay than the Isha prayer. Then, when the Prophet (peace and blessings be upon him) would perform this prayer and come to me, he would offer four or six rak'ahs afterwards, and I never saw him spreading anything to protect himself from the ground. Yes, I do remember that on a rainy day we placed a mat under him, but it is as if I can still see water gushing from its torn place.

(Second chain) There is a similar hadith, with the additional detail that the meaning of "batta" is explained as "al-nat‘", which refers to a leather mat that was spread out for prayer and for eating food.