Sitting Motionless During The Sermon
One should sit quietly and motionless during the sermon. Even necessary talk, as mentioned in the hadeeth (below), makes one lose the reward of Jumu’ah. This proves one should remain still and quiet as one does in salaat. If one fiddles with pebbles, his hair or something else during the sermon, his reward for Jumu’ah is destroyed. Sometimes people distribute papers or flyers during the sermon, thus depriving themselves of their rewards. Nowadays its common for people to toy with their cell phones [or fiddle with anything in their hands]. May Allaah (subhaanahu wa ta’aalaa save us all).
It is narrated by Abu Hurayrah (radiAllaahu ‘anhu) that the Blessed Prophet (sallAllaahu ‘alayhi wasallam) said, “If one of you says ‘be quiet’ to another while the imam is delivering the sermon on Jumu’ah, you have lost the reward of Jumu’ah.”
[Bukhaari and Muslim]
It is narrated by Ibn ‘Abbaas (radiAllaahu ‘anhumaa) that the Blessed Prophet (sallAllaahu ‘alayhi wasallam) said, “The example of a person who talks while the imam delivers the sermon is like a donkey ladened with books on his back; and the one who tells another to be quiet has voided his Jumu’ah.”
It is narrated by Abu Hurayrah (radiAllaahu ‘anhu) that the Blessed Prophet (sallAllaahu ‘alayhi wasallam) said, “Whoever performs ablution, then comes for Jumu’ah, listens to the sermon and remains quiet, all his sins between the two Jumu’ahs are forgiven, plus the additional three days; and whosoever touches a pebble, has committed a foolish act.”
Taken from: “The Essentials of Jumu’a” By Ibrahim Madani, pages 71-72