You must keep your mouth clean.
For that matter, not only gargle but control of speech and control of food is also necessary.
Taken From "Roj Ki Ek Salah" - Book by Acharya Mahashraman
मुंह को साफ रखना चाहिए. उसके लिए कुल्ला ही नहीं वाक्संयम व खाद्यसंयम भी आवश्यक है.