´Abu Hurairah narrated that :` Allah's Messenger said: "If it were not that it would be difficult on my nation, then I would have ordered them to use the Siwak for each prayer."
Hadith Referenceسنن ترمذي / كتاب الطهارة عن رسول الله صلى الله عليه وسلم / 22
´Zaid bin Khalid Al-Juhani said :` 'I heard Allah's Messenger saying: 'If it were not that it would be difficult on my nation then, I would have ordered them to use the Siwak for each prayer and to delay the Isha prayer until the third of the night.'"He [Abu Salamah, one of the narrators] said: Zaid bin Khalid wouId attend the prayer in the Masjid and his Siwak would be on his ear in the location of the pen on the ear of a writer. He would not get up to pray without cleaning his teeth, then returning it to its location."
Hadith Referenceسنن ترمذي / كتاب الطهارة عن رسول الله صلى الله عليه وسلم / 23
Hadith Gradingالألبانی:صحيح، صحيح أبي داود (37) | زبیر علی زئی:إسناده ضعيف / د 47