Answered by Shaykh Sohail Hanif, SunniPath Academy Teacher
How long must one wait while in ruku, or in sajda, or in the sitting position between the two sajdas, before going to the next movement?
Assalamu alaykum
Imam al-Shurunbulali mentions in Maraqi al-Falah in the section of the necessary (wajib) acts of the prayer that it is necessary to pause momentarily in all of the integral elements of the prayer, i.e. the standing, bowing and prostrating.
He defined this brief pause as being a stillness of the limbs such that the joints are all still.
Imam al-Tahtawi in his supercommentary on Maraqi al-Falah explains this as being the length it takes to say subhanallah’ once. [Hashiya al-Tahtawi ala Maraqi al-Falah, 1:340, Maktaba al-Ilm al-Hadith]