Sahih Bukhari 818 — To sit for a while between the two prostrations

Narrated Abu Qilaba: Once Malik bin Huwairith said to his friends, "Shall I show you how Allah's Apostle used to offer his prayers?" And it was not the time for any of the compulsory congregational prayers. So he stood up (for the prayer) bowed and said the Takbir, then he raised his head and remained standing for a while and then prostrated and raised his head for a while (sat up for a while). He prayed like our Sheikh `Amr Ibn Salama. (Aiyub said, "The latter used to do a thing which I did not see the people doing i.e. he used to sit between the third and the fourth rak`a). Malik bin Huwairith said, "