Muslims can erase the sins of the previous week by presenting themselves at their best for Friday prayers, this week's sermon says.
Worshippers must shower, perfume, put on their best clothes and attend prayers if they are to be cleansed of sins - but only if they have not harmed anyone.
The Prophet Mohammed once said: "The five prayers and the Friday to Friday [prayer] are expiations for what was in between."
Allah ordered worshippers to leave behind all else when it was time for Friday prayer, according to a verse in the Quran: "When the call is heard for the prayer of the day of congregation, haste unto remembrance of Allah and leave your trading. That is better for you if ye did but know."
There is an hour on Friday when all dua'as, or prayers, are responded to. But as no one knows precisely which hour, Muslims are encouraged to increase worship and prayer all day.
"There are ethics and manners [to Friday prayer] that Muslims should pay attention to," the sermon says. "These include showering and putting on perfume."
There was an occasion, reported by the Prophet's wife, Lady Ayesha, when worshippers went to Friday prayers covered in dust and sweat. The Prophet Mohammed said to them: "If only you had cleaned up for this day."
Men are urged to go to prayers early, so they hear the sermon.