How to Inform the Imam of the Number of Rak‘ats
Issue No. 1070 - In order to inform the imam, the follower may tap his knee with his hand as many times as the rak‘ats of the prayer have been performed, or say Allahu Akbar, or inform him in any other way, which does not involve talking, or acts that invalidate prayer. However, he should not rise and continue the prayer before the imam.
