Lady Aisha Siddiqa (may Allah be pleased with her) narrates: The Prophet Muhammad (peace be upon him) used to observe (voluntary) fasts to such an extent that we would think he would never stop fasting, and sometimes he would stop observing voluntary fasts to such an extent that we would think he would not fast at all. I never saw the Prophet Muhammad (peace be upon him) fasting in any month more than he did in Sha'ban, except for Ramadan.
Hadith Referenceصحیح ابن حبان / كتاب الصوم / 3648
Hadith Gradingفضيلة الشيخ الإمام محمد ناصر الدين الألبانيصحيح: ق - مضى (3629). تنبيه!! رقم (3629) = (3637) من «طبعة المؤسسة». - مدخل بيانات الشاملة -.فضيلة الشيخ العلّامة شُعيب الأرناؤوطإسناده صحيح على شرط الشيخين