Mukhtasar Bukhari (Abridged) 498 — Using miswak on Friday is Sunnah

Narrated from Sayyiduna Abu Hurairah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings of Allah be upon him) said: "If I had not considered the hardship and difficulty for my Ummah, I would have surely commanded them to use the miswak at the time of every prayer."