Why do the Malikis hold the view that the optional time for the 'Isha prayer extends to one-third of the night, and that the time after it until Fajr is a necessary time?

The disagreement concerning the end of the optional time for the 'Isha prayer is well-known. Its extension to one-third of the night is not exclusive to the Malikis; many scholars agreed with them, even though there is a disagreement within the Maliki school itself, with some holding that it extends until half the night. The origin of this disagreement is the differing prophetic hadiths reported on this matter. What is relied upon by the Malikis is that the optional time for 'Isha extends until one-third of the night, citing hadiths such as Aisha's statement: "They used to pray 'Atamah (Isha) between the disappearance of the twilight and one-third of the night." The disagreement about the last optional time for 'Isha also exists among the Shafi'is and Hanbalis. The cautious approach is not to delay the 'Isha prayer beyond one-third of the night. As for the time after one-third or half the night, it is a time of necessity or permissibility, and it is not a time when the prayer is invalid. The statement of those who say that it becomes a missed prayer (qada') after half the night is incorrect, as the Companions issued a fatwa (definition) that a menstruating woman, if she becomes pure before Fajr, should pray Maghrib and 'Isha, which indicates that the time for 'Isha extends until Fajr. This is the view of the majority of scholars.