How can the hadith "Two-thirds of the people of Paradise are from this Ummah" be understood, given the increasing human population throughout the ages? Does it mean that previous nations were large in number but most of them perished, or does the glad tiding pertain only to the number of those who are saved?

The number of the Ummah of Prophet Muhammad (peace be upon him) is small compared to previous nations, as confirmed by the Almighty's saying: ﴿Has there not come to you the news of those before you - the people of Noah and 'Aad and Thamud and those after them? No one knows them but Allah.﴾ Ibrahim/9. And it was stated in the Hadith: «You are to the people like a black hair on the skin of a white ox, or like a white hair on the skin of a black ox.»

However, despite their small number among nations, they are the most numerous inhabitants of Paradise. The Prophet (peace be upon him) clarified that they will constitute half or two-thirds of the inhabitants of Paradise, and that those who responded to his call are more numerous than those who responded to the messengers before him. The reason for the large number of his followers is that his miracle, the Noble Qur'an, is continuous, preserved, and clear to all generations until the Day of Judgment, whereas the miracles of previous prophets ended with their demise.