Abu Bakra reported God’s messenger as saying, “The months of festival, Ramadan and Dhul-hijja, are not defective.”* *The most probable meaning is that, even if these months have only twenty-nine days, they are not on that account to be considered deficient in comparison with a month which has thirty days. (Bukhari and Muslim.)
Hadith Referenceمشكوة المصابيح / كتاب الصوم / 1972
Hadith Gradingالألبانی:مُتَّفَقٌ عَلَيْهِ | زبیر علی زئی:متفق عليه
Hadith Takhrij´تحقيق و تخريج: محدث العصر حافظ زبير على زئي رحمه الله` «متفق عليه، رواه البخاري (1912) و مسلم (1089/31)»