It was the practice of the Prophet (peace and blessings be upon him):
"When he (peace and blessings be upon him) entered his house, the first thing he did was use the miswak."
Hadith Referenceصحیح الجامع الصغیر / حرف الكاف / 4717
Hadith Gradingالألبانی:صحيح
Hadith Takhrij[م د ن هـ] عن عائشة. مختصر مسلم ١٢٣، صحيح أبي داود ٤١، الإرواء ٧٢.