مَنْ تَوَضَّأَ يَوْمَ الْجُمُعَةِ فَبِهَا وَنِعْمَتْ، وَمَنِ اغْتَسَلَ فَهُوَ أَفْضَلُ
Translation: Whoever makes wudu on Friday has done well, and whoever bathes has done what is better.
The majority use this as evidence that Friday ghusl is recommended and superior, but not a condition for the Friday prayer's validity.