Riyad Us-Saliheen (Gardens of the Righteous)

Chapter 312
Undesirability of Sitting with Erected Legs during Friday Sermon

1705. Mu`adh bin Anas Al-Juhani (May Allah be pleased with him) said: The Prophet (PBUH) forbade (us) from sitting with our legs drawn up to our belly (Ihtiba') during the Friday Khutbah (religious talk before the prayer).
[Abu Dawud and At-Tirmidhi].

Commentary:  Habut is the root word of Ihtiba' which means to sit in such a position that the two knees are joined by means of the hand or some cloth with one's belly. To sit in this style during the Friday sermon is not desirable because it causes drowsiness which in turn interrupts the sermon. It must be remembered that listening to the Friday sermon is obligatory and drowsiness during the course of the sermon is likely to disturb it and can also spoil Wudu' which is a prerequisite for the validation of Salat.