Sufyaan [ibn Uyayanah] narrated to us from Abdullah ibn Deenaar that he heard Abdullaah ibn Umar say, “I heard the Prophet (peace be on him) say while he was on the minbar,
“Whoever among you comes to [the mosque to offer the] Jumuah prayer, let him perform ghusl.”
(Musnad Ahmad, Vol. 2, p. 37. The isnaad of this Hadeeth is saheeh according to the conditions set by al-Bukhaaree and Muslim.)
Commentary
Performing ghusl on Friday (Jumu’ah) in preparation for the Friday prayer is a highly recommended sunnah. Some scholars have gone as far as to consider it obligatory based on this and other ahadith, such as the one in which the prophet (peace be on him) said, “Performing ghusl on Friday (Jumu’ah) is obligatory upon every adult Muslim.” However, other ahadith and reports from the companions reduced this obligation to the level of being a confirmed sunnah (sunnah mu ‘akkadah).
Source:
Thulaathiyyaat Musnad Ahmad ibn Hanbal (may Allah have mercy on him)
Reports of Imaam Ahmad that have only three narrators between him and the Prophet, peace and blessings be upon him.
Shaykh Muhammad ibn Ahmad ibn Saalim as–Saffaareenee al–Hanbalee ~(1114 –1188 AH)