As for that which Muhammad ibn al-Husayn ibn Abi al-Khattab narrated, from Muhammad ibn Ismail, from Muhammad ibn Yaqub ibn Shuayb, from his father, who said: I (narrator) said to Abu Abdillah عليه السلام: “The people say that the Messenger of Allah سبحانه وتعالى, fasted twenty-nine days more often than He صلى الله عليه وعلى آله وسلم fasted thirty days.” Imam عليه السلام said: “They have lied. The Messenger of Allah سبحانه وتعالى, may Allah سبحانه وتعالى bless him and his family, did not fast except completely (thirty days), and that is the saying of Allah سبحانه وتعالى the Exalted: ‘So that you may complete the prescribed period.’ Thus the month of Ramadan is thirty days, Shawwal is twenty-nine days, and Dhu al-Qadah is thirty days; it never decreases, because Allah سبحانه وتعالى the Exalted says: ‘And We سبحانه وتعالى appointed for Musa thirty nights.’ (Surah Al-A'raf 7:142) And Dhu al-Hijjah is twenty-nine days. Then the months are upon the like of that: a complete month and a deficient month. And Shaban is never complete.”