What is the basis for the majority's opinion that a menstruating woman, upon becoming pure after 'Asr, must pray Dhuhr and 'Asr?

If a menstruating woman purifies herself before sunset, the prayers of Dhuhr and Asr become obligatory upon her, according to some Companions and the general body of the Tabi'in (except for Al-Hasan Al-Basri). According to the Malikis, for both prayers to be obligatory, there must remain a time sufficient for five rak'ahs before sunset; otherwise, only the Asr prayer becomes obligatory. The time for Dhuhr prayer for a menstruating woman extends until sunset.