The Prophet, sallallaahu 'alayhi wa sallam, saw some women who told him that they were the good and beautiful wives of righteous men who were pure and never become defiled, and that they live without aging and are immortal and will never die. Who are these women?

All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

The women in question are the Hoor. Al-Haafith Ibn Katheer, a Shaafi‘i scholar said that in a Hadeeth on the authority of Anas ibn Maalik the Prophet asked his Lord, to show him the Hoor. The angel Jibreel (Gabriel) descended and showed him the Hoor. The Prophet attended to them and greeted them with Salaam and they replied to his greeting. He asked them about themselves, and they informed him that they were good and beautiful women and the wives of righteous men who were pure and would never become defiled, and that they live without aging, are immortal and will never die. 

Allaah Knows best.