Surah 33. Al-Ahzab, Ayah 29

When, immediately after their revelation, the Prophet recited the above two verses to his wives, all of them emphatically rejected all thought of separation and declared that they had chosen "God and His Apostle and the [good of the] hereafter" (recorded in several compilations of ahadith, among them Bukhari and Muslim). Some of the earliest Islamic scholars (e.g., Qatadah and Al-Hasan, as quoted by Tabari) held that the subsequent revelation of verse {52} of this surah constituted God's reward, as it were, for this attitude.

They were all well-doers. But being in their exalted position, they had extra responsibility, and they had to be specially careful to discharge it. In the same way their reward would be "great", for higher services bring higher spiritual satisfaction, though they were asked to deny themselves some of the ordinary indulgences of this life.