With this hadith, he said in it, "When you perform ablution, rinse your mouth."
حدثنا محمد بن يحيى بن فارس حدثنا أبو عاصم
بهذا الحديث قال فيه إذا توضأت فمضمض
No references are available.
[Its chain of transmission is sahih] Bayhaqi narrated it: 1/52, from the hadith of Abu Dawud, through the same chain.