Mishkat al-Masabih 7 Fasting كتاب الصوم 16

وَعَنْ أَبِي بَكْرَةَ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: ” شَهْرَا عِيدٍ لَا يَنْقُصَانِ: رَمَضَانُ وَذُو الْحِجَّةِ ”

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.)