It is narrated from Sayyiduna Tamam bin Abbas (may Allah be pleased with them both) that once some people came to the service of the Prophet (peace and blessings be upon him). The Prophet (peace and blessings be upon him) said to them: "What is the matter? I see your teeth are yellowish. Use the miswak. If I did not fear hardship for my ummah, I would have made the use of miswak obligatory for them just as I have made wudu obligatory."