Lady Aisha Siddiqa (may Allah be pleased with her) and Lady Umm Salama (may Allah be pleased with her), who are the wives of the Prophet Muhammad (peace be upon him), both narrated this. The Prophet Muhammad (peace be upon him) would sometimes be in a state of janabah (major ritual impurity) at the time of true dawn during Ramadan, not due to a wet dream, yet he would still observe the fast.
Hadith Referenceصحیح ابن حبان / كتاب الصوم / 3489
Hadith Gradingفضيلة الشيخ الإمام محمد ناصر الدين الألبانيصحيح: ق - انظر ما قبله بحديث.فضيلة الشيخ العلّامة شُعيب الأرناؤوطإسناده صحيح على شرطهما