Is it valid for a married couple to fast in Ramadan if they sleep in a state of janabah (ritual impurity), and what is the maximum time allowed to remove janabah? And how is the statement of Lady Aisha to be interpreted, "that the Messenger of Allah, may Allah’s prayers and peace be upon him, when he slept in a state of janabah, he would wake up fasting and then perform ghusl (ritual bath)," while he maintained performing the Fajr prayer on time?

It is permissible for spouses to sleep while in a state of janabah (definition), and their fasting remains valid. The maximum time for delaying ghusl (definition) is the entry of the prayer time for those for whom congregational prayer is obligatory, or before the end of its time by a sufficient duration to perform ghusl and the prayer for those for whom congregational prayer is not obligatory, because ghusl is a condition for the validity of prayer. The Prophet, peace and blessings be upon him, would be overtaken by dawn while in a state of janabah, then he would perform ghusl, fast, and pray on time.