From Sahih Bukhari (Hadith 903):
Narrated Yahya bin Sa`id:I asked `Amra about taking a bath on Fridays. She replied, " Aisha said, 'The people used to work (for their livelihood) and whenever they went for the Jumua prayer, they used to go to the mosque in the same shape as they had been in work. So they were asked to take a bath on Friday
Reference: Bukhari 903