What is the ruling on the session of rest?

The jalsat al-istirahah (rest session) is recommended. It is a light sitting after the second prostration and before standing up in every rak'ah (unit of prayer) that is not followed by a tashahhud (testification of faith). It has been authentically reported in Sahih al-Bukhari and Sunan Abi Dawud and al-Tirmidhi. It is considered a Sunnah (prophetic tradition) by Imam Shafi'i, Ishaq, and Ahmad. It is not prescribed after a prostration of recitation (sujud al-tilawah), nor for one praying while sitting, nor in the rak'ah that is intended to be followed by a tashahhud, unless one intends to omit the tashahhud. It serves as a brief pause between two rak'ahs, and it is best that its duration does not exceed the length of طمأنينة (tranquility/stillness).