It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said on one of the Fridays: "O community of Muslims! Indeed Allah has made this day an Eid for you, so take a ritual bath and hold firmly to the use of the tooth-stick (siwak)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 1427